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Honda MR175 Elsinore - points / ignition help please

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Hi there,

 

Thanks for taking the time to read my question.

 

I am a little confused with the wiring on my Honda - any help greatly received!

 

The manual advises checking the points gap by rotating the engine and using a battery/bulb to see when the light goes out.

 

The bulb on mine doesnt go out even when i open the points manually.

 

The wiring diagram seems to indicate that the points and ignition coil are both earthed.

 

The other end of the coil seems to be wired to the isolated part of the points. If this is right then I dont get how the bulb would ever go out - as it always has an earth path independant of the points?

 

As advised in the manual - the battery / bulb checker is used as follows - negative from battery to earth. Positive to bulb, then other side of bulb to stator wire (yellow / black on the mr175)

 

Can someone please explain the wiring of the ignition coil relative to the points?

 

Thanks again

 

 

Kirk

Edited by Kirk123

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Hello fellow MR 175 owner. Are you trying to get this bike to run or just tuning it up?

 

I will be honest that in my experience trying to get the stock points to work unless it is a new ignition is a waste of time.  Even from new this ignition was of poor quality and didn't last long without starting to cause problems due to a poor design of the flywheel and fast wear of the points cam surface.  I'm not one to ask about using the light method to time the engine because I never could get it to work either (on my XR75) and the reason that it didn't work was because the ignition was worn out.  Of course checking the wiring diagram in the shop manual versus what is on your bike would be a good first step.  Bad grounds can always be an issue along with broken wires (internal) so checking continuity is also helpful from circuit to circuit.  There are new flywheels (the source of many of the problems) on eBay from time to time but they are hard to find since they were used up over the years to fix the ignition.  I've never seen the stock NOS stator coils for sale but I'm sure that someone can rewind them for you. 

 

I solved this problem by finding a CR 125 (1974-78) stator, flywheel and coil and installing it on the MR 175.  Everything bolts up fine and this ignition transforms the bike (thanks to Ray Ivers for his advice on this).  If you want lighting then Powerdynamo offers a complete system with lighting coils that I've installed on one of my MR's that works great but this is a much more expensive solution and converts the bike to 12 volts, a real plus in my opinion.  Also, PVL offers a fantastic ignition that would work well but I have no experience with it.

 

All the Best!

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Hi There,

 

Thanks so much for the reply. I have rebuilt the bike from a wreck so am trying to get it running, before starting to improve the bike. I have a 74 CR125 running electronic ignition - so this is probably the way to go! I will look up powerdynamo - that sounds a good system! Have you done anything else to the bike? Mines Stock at the moment. Im in the UK so the bike is very rare here - has cost a bit in parts from the states!

 

I also have my original XR75 from when I was 5! need to get that running again next!

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Hi Again,

 

Would you be able to tell me where the best place to buy an ignition?

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We've often wondered if the MR 175 was exported to the UK - sounds like it was.  For ignitions you can go directly to Powerdynamo's web sight and request a quote.  http://www.powerdynamo.biz/eng/systems/7743/7743main.htm.  I have one complete but modified MR 175, a second stock one that is in parts (except the engine) and my current project is converting a MT 125 to dual purpose use using a modified MR 175 engine with the Powerdynamo ignition.  The title was lost on the MT so I'm having to get a new one so that I can ride on the street - the rules for converting dirt bikes to street use in the state of Iowa make it nearly impossible unless you're starting with a street legal bike.  From what I can tell the MT125 is almost identical to the MR with some minor changes made to the frame for street use.  All of the MR parts will interchange on the MT frame and vice versa.

 

If you do a search in the Thumper Talk Vintage section for the MR 175 you should find a lot of postings on modifying this bike.  I've been working closely with Ray I. and we've been able to find a source to rebuild the crank (Crank Works) with parts from a KDX 175, ignitions, suspension upgrades (1978-1981 XR 185/200 front forks work on the MR triple clamp and work much better than stock), transplanting the MT 125 transmission to clean up the big gaps in ratios from the stock MR, Clarke plastic gas tanks, Works Performance shocks (or maybe Falcon in the UK).  Ray has been responsible for almost all of the research to improve and modify the MR engine and chassis.  He's published specifications on porting, fuel systems and modified OEM exhaust pipes that really make this engine come alive. 

 

Greg

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Hi Greg,

 

Thanks for this information - I will certainly do the search as recommended.

 

I have rock shocks on the back of the bike. The bike is standard at the moment apart from that.

 

The MR, as far as I know, was not imported to the UK. My bike is an American import - as is my CR125 (although the CR was available). It was in a fairly ropey state when I bought it - but thats part of the fun.

 

It does make part location a challenge - however we do have David Silver in the UK - and have you heard of CMSNL? they stock a fair amount of NOS parts for most Japanese bikes.

 

I would love to do another engine for the MR175 - and often watch for items for sale that can be sent through. 

 

I also do modern Enduro - I notice your KTM - I have a Crf250x at the moment - Im not as young as I used to be so an electric start is required!

 

 

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Hello Kirk,

 

You are very welcome for the information - I'm impressed that you imported the MR into the UK.  Are their others in the Country? What was it about the bike that you liked?  Do you ride in vintage events?

 

I have purchased many high priced parts from CMS in the Netherlands over the years but it's hard to beat their availability of rare parts.  I've never found much available at David Silver Spares, at least in their US location, for the MR.  Most of my parts have been purchased on eBay.  If you are patient the parts you need often show up.

 

If you need any engine parts in particular feel free to let me know, I have some in my garage.

 

I'm not so young either (I could have bought an MR back in the day if I had known that they existed) and have also purchased electric start only bikes for awhile now.  I've owned a 2009 CRF250X and thought it was a wonderful bike and would love to have another.  The KTM's have been a favorite of mine for awhile but I have owned many more Honda's over the years, since the beginning actually starting with a 1972 Z50.

 

Greg

Edited by IAoffroader

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Hi Greg,

 

There are a number of "specialist" importers in the UK who seem to make a living in bringing over bikes from the States - both for parts and immaculate.

 

I saw a guy offering a Mr175 and was taken by its looks and originally thought it may be useful if only for parts for my CR125.

 

The bike was in a state - but had the basis for a good restoration - so I thought it may be worth having a go at restoring it. Its nearly finished - Ill post a picture if you like. I have a soft spot for Honda - and in particular 70s and 80s motocross / enduro and trials. I think the soft spot comes from my first bike which was a XR75. I still have it and its next on the to do list! Is trials big in the US?

 

I'm aware that there may be a few other MR175s in the UK - as I have definitely seen one for sale.

 

Thanks for the offer of parts - I will have look at what I need as spares are not so easy in the UK. I would like a whole engine as a spare (and to try out the mods you have kindly suggested) so if you see one come up I would be interested.

 

I have raced enduro for about 10 years and started on a KTM. They are great bikes - and I had a two stroke so perfect to work on. I then changed to a four stroke as it was more suited to the type of events we get here (MUD!) - and at the time the two strokes were always very peaky. I started with the R version, but swapped to the X for the electric start.

 

O and Ive always loved the Z series bikes!

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Kirk,

 

Thanks for sending the photo.  Very nice - you are doing a first rate restoration on your MR!  That is interesting about the importation of bikes from the US - I would think shipping alone would be a couple of hundred pounds.  Do you have an engine for your MR?

 

I purchased my second MR mainly to get spare parts and the engine.  Unfortunately the engine had some case damage from loose mounting bolts (I guess) but it had been repaired nicely.  The engine ran nicely once I replaced the ignition with the Powerdynamo unit.  The frame had also been repaired but was still very solid.  I've noticed on eBay that trying to buy a complete engine is hard - most sellers want to part it down to the last  little screw and those that don't ask a lot of money for engines that are in unknown and probably worn out condition.  My thought would be to try and find a matched set of used solid cases and a good used crankshaft as the basis for a "new" engine.  Since we have settled on the later MT 125 transmission as the way to go and they are readily available at low prices and don't seem to be worn out or broken.  Most of the smaller internal parts are available used or new. Unfortunately, at least one of the transmission needle bearings is very hard to locate.  

 

i will keep my eyes out for a complete engine or bottom end.

 

By the way - how do you like the Rock Shocks?  Have you had any experience with Falcon shocks?  I was interested in Falcons for my MT 175 project and they have a distributor in the US.

 

Trials isn't huge in the US but it has a strong dedicated following.  There is also a strong interest in the twin shock vintage trials bikes.  I owned a Suzuki RL250 for awhile but found it uncomfortable to ride honestly although the engine was great.  My KTM 450 had more low end torque and was much more comfortable!

 

I have two 1982 Z50R's,l one heavily modified and one pretty stock so I love the Z50's also.

 

Take Care,

Greg

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Hi Greg,

 

I'm sure shipping to the UK would be at least that - I think the guys ship a container - and then the cost is split down against how tightly you can pack the bikes / parts in. There is also duty to pay.. which is never very nice!

 

However some of the bikes imported are rare and I think the prices in the UK probably reflect that. Also, you have much better weather than we do - so rust doesn't seem such a problem!

 

I will certainly take your advice with respect to the engine - I would like to build one up following your recommendations - so will keep my eye out for the parts - particularly the transmission etc.

 

I do have the engine for the bike in the picture. So far its had a rebore and replacement piston and rings and a new clutch - and all the other parts checked. I was struggling with the timing - hence the original question. I have sorted that now - and the engine is almost ready to go back in to the bike. Once I have the bike running I will think of the great mods you have suggested - and hopefully build a second engine which can drop straight in. 

 

I have used rock shocks within trials  and I like them. For me simple is always good - and the person who makes them (John Bull) is very helpful and sells all the bits. The shocks can be rebuilt at home which adds to the appeal - and they are a bit cheaper.

 

I have had a bike with Falcons on - and they are probably a better action - using gas to keep things a bit more stable. They are rated highly - but mine leaked - and are more difficult to rebuild in my opinion. They are however fully set up for your weight and style and like I say are well respected here in the uk. We are also seeing a few other premium items coming to the market - Ohlins of course, but also magicals and maxton are now producing some rebuildable items (not cheap though).

 

My CRF is on standard suspension, but reworked for my weight. Its far better than I am!

 

One question, I do have a second pipe that came free with the bike when I bought it. Looking at the picture of yours in your "garage" I think its the same (I think its called Bassini?). Do you recommend this pipe? I have repacked it (although got a little confused as there seems to be a bit of free space behind the end cap which I think is taken up by a spring?) - and just need to work out how to mount it. I was tempted to put the standard pipe on to begin with and then swap parts one at a time.

 

I do intend to compete on the bike, although against some of the specials I see racing in the vintage class - I dont think I will do so well - but its about riding a bike I think is great rather than winning!

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Kirk,

 

Sounds like you have a good engine that should work well.  Hopefully your points set-up will work OK for you, at least initially.  I've been collecting the hard to find parts for this engine since that seems to be never ending activity for those of us building the MR and CR engines since they share so many parts.  I've been fortunate to have the help and knowledge of an expert on these Honda's to help me along.

 

Thanks for the shock information.  A friend uses YSS shocks that evidently are excellent as well.  I would love to have a set of Ohlins but they are very hard to find in the US. A company called VMX Racing (http://www.vmxracing.com/) sells an Ohlins type shock that looks very interesting as well.  This company sell excellent reproductions of the CR vintage plastic which i used on my MR since the OEM plastic that I have looks pretty bad.  I've used Works Performance shocks on three of my vintage bikes now and they are excellent quality and performance but somewhat pricey.

 

For the engine I'm running now I had the lower end built by Klemm Vintage based in Arizona.  I had two cylinders ported, one to specifications developed by the MR expert, Ray, and the second to Klemm's specifications.  This was before I was comfortable assembling the bottom end myself.  With the carburetor, cylinder porting, head modifications and exhaust this engine can exceed 30HP and has excellent torque across the RPM range, it's really quite amazing.  One of the keys is getting the compression ratio up which requires a modified head and possibly cylinder machining.  With these engine modifications suspension improvements become even more important.

 

You are correct that the pipe I'm using currently is a Bassani and it is probably the best of the vintage expansion chambers in my opinion and is fairly quiet as well. The negative is that it sticks out a fair amount and interferes with your right leg, but all of these vintage and new chambers do the same.  I don't remember a spring in the end cap to be honest, I think mine is filled with fiberglass to the end cap but I could be wrong.  There is a guide to modifying the stock MR exhaust that makes it superior to any vintage aftermarket pipe  that is detailed on Thumper Talk, or used to be.  It requires a MT 125 header and some welding skills to pull off but in the end gives you the highest performance possible and a nicely tucked in pipe.  The internals of the OEM MR pipe as designed by Honda were perfect for this engine (other than the MR 175 header pipe) but when the baffles were installed it limited the performance capability of the pipe.

 

The modern and even Evo bikes suspensions are great - I've been toying with the idea of modifying an Evo type frame (1980's long travel dual shock or even mono shock type) to work with the MR engine but that probably won't happen anytime soon.  The CRF250X suspension is excellent and when tuned to the rider makes the bike a blast to ride I'm sure. Riding the vintage bikes takes a different mind set for sure.

Edited by IAoffroader

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Hi Kirk (Greg too),

 

Your bike looks great!  I can't remember the last time my MR was actually that clean, if it ever was... I bought mine for parts too, funny how plans change.

 

You're in very good hands with Greg, as he and I have been trying to get the most out of this bike for some time now.  As far as suggestions go - if you're looking to keep things relatively simple and the bike's stock appearance, I'd go with the CR125M ignition as mentioned, a semi-gutted MR175 pipe (the spark arrestor and tailpipe insert can stay, but the internal baffle/tube must be removed), a .010" head gasket, and the MT125 transmission.  You can expect about 20% more power everywhere and a much more quick-revving and responsive motor, plus at least an additional 30% more power at the transmission shift points.  An owner of a stock MR175 would not recognize this motor, yet the cylinder, head, and carb are OEM.

 

I've done many other mods, some of which Greg mentioned - a bunch are represented on my Photobucket album:

 

http://s399.photobucket.com/user/rayivers/media/Motorrightside.jpg.html

 

If there's anything you're curious about just ask, it may well be something I've already tried - maybe more than once. :)

 

Ray

 

 

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Thanks Ray / Greg,

 

What a stroke of luck to meet you both!

 

I will get the bike up and running and then its definitely time to build another engine - or indeed modify the one I have.

 

I dropped the engine in over the weekend - have to say it seems to sit more to one side than i remember! but the bolts all line up so I should probably take more notice when I take things to bits! I also wired the bike in, so a few more jobs before I can see if it works! I will do a video of the first start... may be worth a laugh!!

 

I like the thought of electronic ignition - I have it running on my CR - but I want to keep the lights running. I have been in touch with Powerdynamo - and will see what happens.

 

Is the gasket you mention readily available? I always struggle here in the UK for parts - but have had excellent service from the US.

 

Im also on the look out for the MT transmission - could I please ask - does it drop straight in?

 

What great pictures and brilliant information! I will have to take my time and go through these bits nice and slowly.! and what a great idea with the pipe! I think Ill run the standard pipe to get the bike running - and then run the aftermarket one while I modify the stock one.

 

I also am running a twinshock honda trials at the moment - I realise this isnt such a big think in the states - but have you seen the RS series of bikes? Mine is running an XR engine at the moment - and montesa 315 front forks (as the suspension is better and I can run a disk in local non twinshock classes). I have made a set of "fiddle forks" for the bike (in the UK we are allowed to run modified internals if the outside looks the same - I took a set of TL forks and fitted more modern forks. The are very similar to the MR - so they may end up on the bike yet!

 

Looks like your both interested in all types of bikes, but favour motocross? do you compete?

 

Great to meet you both and again thanks for all your help this far!

 

 

Kirk

Edited by Kirk123

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Kirk,

 

I had to shim all my Honda motors (CR125M and MR175) with washers, otherwise the frame and/or mounting brackets would bend.  Honda did not do this, and I think this is why my MR's top LH mounting bracket snapped off.  The MR frame required one washer at that location, the CR frame needed two (top RH and bottom front RH).  It's possible you might not need any, but I would check to be sure.

 

I found a U.K. place that should be able to make the gaskets for you (they'll need a sample;:the 12251-373-000 original gasket is for up to .5mm OS bores, the 12253-373-000 is for .75mm OS and up - there's also a 12251-373-405 gasket that may be thinner, I don't know):

 

http://www.stephensgaskets.co.uk/product/cylinder-head-gaskets

 

I used Cometic Gaskets and Lubbock Gaskets here in the US, both worked out fine.  Copper head gaskets love to leak; I use liquid copper-based sealant and overtorque slightly, and ended up machining a .001" raised ring in the head at the bore edge to concentrate pressure there.

 

Yes, the MT125 transmission will drop right in.  I believe Greg is using the complete MT gearset, and I used an MR175 5th gear instead of the MT one which works fine so far.

 

I raced MX and scrambles back in the 70's, but honestly never really liked it much.

 

Ray

 

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Thanks Ray, I have shimmed the top back mounting with a couple of washers. This mount had originally broken so I welded it back straight (and hence maybe needing an additional shim).

 

Engine dropped straight in so I assume its in right - just seems a little over to one side when looked down upon.

 

Carb cleaning currently in progress - which hopefully will go back on this weekend.

 

Thanks for the gasket tip - will follow it up!

 

Thanks Again

 

Kirk

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Ray is correct - I'm running the early large shaft MT 125 transmission gear set in my modified MR. There were two different main shaft diameters used on the MT - the early (through most of 1975 I believe) is a larger diameter than the later main shaft.  The later mainshaft is the same diameter (but not the same part number due to the different 1st gear) as the 1975-1976 MR 175.  The 1977 MR 175 uses a completely different mainshaft part number than either the MT or early MR.  The issue with the early mainshaft is that a specific, somewhat hard to find, clutch basked is required to work with this part.  The later small diameter mainshafts use the MR/CR clutch baskets which are more common.  The gears are all the same so they interchange from year to year from what Ray has figured out.

 

On my new engine I will run a hybrid transmission, using the MT 1-4 gears and use the MR 5th gear set. 

 

I had an opposite problem with my MT frame - the engine was too tight and wouldn't fit between the frame mounts without some modification.  I didn't know that you were running a shim in between the frame and engine mounts Ray.  Maybe the MT 125 engine was slightly narrower than the MR but that seems unlikely. 

 

Everytime I look at photos of Ray's bikes I'm impressed.  I've never raced in a sanctioned event although an enduro still has some apeal, if it's not muddy! 

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Hi Greg,

 

Thanks for the information definately the later transmission for me then!.

 

The top frame mount at the back had broken on mine - and the other side seems to be different to the manual (which seems to talk about a removable plate) - mine is a simple mount on both sides. I welded the frame back straight but then there is a gap which I have shimmed.

 

Bike nearly finished - and now im a bit confused on one of the simpler jobs - there is a breather - i think for the transmission which has a long pipe. Im not sure where this goes? does it go upwards and into the frame? all my other bike breathers seem to just hang down by the swingarm.

 

Also have you changed your jetting? My carb is in bits so good time to check///

 

Have to say we have little choice abou mud here in the uk. I was riding in wales at the weekend and we got stuck in the woods!

 

Speak soon

 

Kirk.

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Hi Again.

 

Im a bit stuck.

 

I dont seem to have (or have lost) the needle retaining clip for the carburetor.. any ideas on where I may be able to get one?

 

Thanks

 

Kirk

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Kirk - I want to correct a mistake I made on the clutch parts used on the early MT main shaft.  It isn't the clutch basket that is different from the later MT's, CR and MR, it is the clutch center (which seems even harder to track down).  All of the other clutch parts are interchangeable between the MR & CR.  Based on Ray's experience we like using the straight cut CR clutch main gear and clutch basket set-up on our engines.

 

As far as the carb is concerned Ray is the expert in this area and has done extensive research on jetting specifications.  Based on his research he recommends a 138-140 main jet, 48 pilot & 3.5 throttle valve. Stock main jet is 122, throttle valve is 3.0, & pilot is 52. I've been using the 1974-75 CR125 needle set that seems to be the correct one to use for the modified engines.  These settings will work well on a modified engine, but you may want to stick with close to the stock settings on a stock or near stock engine and Ray may have some thoughts in this area.  My MR is running a litle rich with these settings so I'm going to do some tuning to see if I can get it leaned out.

 

I ran my breather upwards into the air box area but according to the factory shop manual all breather tubes (crankcase, carb, ignition) run down along the back of the engine and fit through the welded wire organizer on the frame.

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