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2005 RM250 total rebuild


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Hi guys!

 

I haven't really been posting much on here, just been reading up on the sport and the bikes a little after a very long break (been riding roadracing GP125).

 

Anyhow, I've never really let go of the MX world, been to the Swedish MXGP round most years, and also been restoring a few bikes, recently a pair of Yz250f's and a WR450 just to make a few bucks and help my friends.

 

Got myself a 2008 RM125 in the spring of 2014, and been riding a little, but the time to ride is very linited due to family life and getting our countryside place in shape. Love the little 125, though.

 

Now I'm rebuilding a 2005 RM250, and I'm trying hard to be very seriuos about this one, I want each and every part to be as good as new or better.

 

The rolling chassis is close to being finished, and now it's time for some engine work. Bought the bike without the engine, and got an ebay replacement bottom end with good cases and a good tranny. Been sourcing the rest off ebay for a couple of months,and now everything is here (except for the transmission small parts and trans bearings), waiting for assembly. Everything is cleaned and inspected, so let the fun begin!

 

Started this engine build by dropping every single bearing out of the cases, and a very thorough cleaning.

hrc wheels rs125 038.jpg

hrc wheels rs125 036.jpg

hrc wheels rs125 037.jpg

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No secret chemicals here, boys. Glass bead blasting. Never, ever do this unless you're removing every single part from the bare cases afterwards, though!!! It takes a LOT of patience and electrical cleaner+compressed air to get the tiny glass grains off the cases, out of every bolt hole and thread.

 

 

I like the surface the soft glass leaves, easy to keep up, and 100% free from any dirt or corrosion.

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Engine assembly time! All parts very clean, almost like cheating..! I'll cut the combustion chamber for correct volume and squish band width/clearance (to run 99 octane pump gas) after the top end has been built.

 

I haven't even looked inside the carb yet, but expect to play the jetting game later on. Suggestions welcome (from people very familiar with these bikes) for 50-80 degrees F, 300ft elevation? PC works/304 combo, mx only.

 

Cheers/

 

Lasse

hrc wheels rs125 040.jpg

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Engine assembly time! All parts very clean, almost like cheating..! I'll cut the combustion chamber for correct volume and squish band width/clearance (to run 99 octane pump gas) after the top end has been built.

 

I haven't even looked inside the carb yet, but expect to play the jetting game later on. Suggestions welcome (from people very familiar with these bikes) for 50-80 degrees F, 300ft elevation? PC works/304 combo, mx only.

 

Cheers/

 

Lasse

 What brand of crank did you buy and main/bearings seals/gasket?

 

thanks

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 What brand of crank did you buy and main/bearings seals/gasket?

 

thanks

I got myself a Hot Rods crank assembly, since the on the OEM crank one of the main bearing surfaces had taken a beating in a seizure before I took care of the bike. Otherwise I'd have for sure rather have rebuilt the OEM unit, but from what I've read the HR cranks should be OK. Main bearings will be OEM Suzuki (koyo/NTN/timken brand).

 

Upon receiving the HR crank I had it measured for trueness, and found a runout of over 0,02mm, which is borderline OK, but not good enough in my book, so I had them trued accordingly. Now it's spinning at less than 0,005mm out of true. The very tiny force needed for an adjustment like this really gives new understanding to why it's important to handle a bare crank very gently during engine assembly.

 

Time will tell if this crank is good or bad..!

 

I also bought OEM seals for the entire engine, but gaskets are from Vertex.

 

/Lasse 

Edited by Southwick
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I got myself a Hot Rods crank assembly, since the on the OEM crank one of the main bearing surfaces had taken a beating in a seizure before I took care of the bike. Otherwise I'd have for sure rather have rebuilt the OEM unit, but from what I've read the HR cranks should be OK. Main bearings will be OEM Suzuki (koyo/NTN/timken brand).

 

Upon receiving the HR crank I had it measured for trueness, and found a runout of over 0,02mm, which is borderline OK, but not good enough in my book, so I had them trued accordingly. Now it's spinning at less than 0,005mm out of true. The very tiny force needed for an adjustment like this really gives new understanding to why it's important to handle a bare crank very gently during engine assembly.

 

Time will tell if this crank is good or bad..!

 

I also bought OEM seals for the entire engine, but gaskets are from Vertex.

 

/Lasse 

Thanks for the reply, let me know how the build goes and the outcome. 

 

Fixin to start in on the top end in my 2004 RM250  myself.

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Got myself a rolling chassis. Galfer 270mm frront disc, Brembo master cylinder mated to Venhill line and a brand new Nissin caliper. Renthal Twinwall, PC works/304 combo. Acerbis chain guide, Sunstar sprockets, DID ER  Series non o-ring chain. Powder coated frame +  shock spring, Acerbis plastics. New OEM rear brake disc, new Excels on OEM hubs/spline drive spokes. Rebuilt suspension front and rear, all new bearings all over. New radiators.

 

Should be nice.

 

And, lastly, a little two stroke trivia; anybody recognize these engine cases? Hint: these can be really fast ones.

 

Cheers/

 

Lasse

hrc wheels rs125 055.jpg

hrc wheels rs125 052.jpg

hrc wheels rs125 054.jpg

hrc wheels rs125 057.jpg

hrc wheels rs125 061.jpg

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Got myself a rolling chassis. Galfer 270mm frront disc, Brembo master cylinder mated to Venhill line and a brand new Nissin caliper. Renthal Twinwall, PC works/304 combo. Acerbis chain guide, Sunstar sprockets, DID ER  Series non o-ring chain. Powder coated frame +  shock spring, Acerbis plastics. New OEM rear brake disc, new Excels on OEM hubs/spline drive spokes. Rebuilt suspension front and rear, all new bearings all over. New radiators.

 

Should be nice.

 

And, lastly, a little two stroke trivia; anybody recognize these engine cases? Hint: these can be really fast ones.

 

Cheers/

 

Lasse

Where did you get the shroud decals from they look good and the blue see cover!

 

Looks sharp still thinking on the 2 stroke case reed inducted.

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  • 2 weeks later...

Engine assembly. Home made crank pulling tool, and clutch center holding tool makes the job easy.

 

I have a question regarding crankcase alignment, though; when I finished bottom end assembly, and was getting ready for the top end, I noted, to my disgust that the cases don't really seem very well aligned. Looking at the cylinder base mating surface, there's a distinct difference in height between the right and left case halves, I'd guess perhaps 0.2mm. I'm not really used to Suzukis, but this is way more than I recall any engine I've ever assembled. I'm worried about cylinder/crankshaft alignment and base gasket sealing.  Thoughts on this?

 

And before you even ask, yes of course both locating dowels are there. Otherwise happy times!

 

/Lasse

 

 

rm250 2005 002.jpg

rm250 2005 006.jpg

rm250 2005 007.jpg

rm250 2005 011.jpg

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Any progress on the rebuild, what paint did you use on the frame.

 

thanks

I pulled the cases apart again, ordered new locating dowels, and I'll have the cylinder base surface/main bearing seats blueprinted before proceeding. Can't finish this engine assembly unless I feel everything is 100% OK. Frame was powder coated in some  dark grey metallic somewhat resembling the OEM paint.

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Got myself a rolling chassis. Galfer 270mm frront disc, Brembo master cylinder mated to Venhill line and a brand new Nissin caliper. Renthal Twinwall, PC works/304 combo. Acerbis chain guide, Sunstar sprockets, DID ER Series non o-ring chain. Powder coated frame + shock spring, Acerbis plastics. New OEM rear brake disc, new Excels on OEM hubs/spline drive spokes. Rebuilt suspension front and rear, all new bearings all over. New radiators.

Should be nice.

And, lastly, a little two stroke trivia; anybody recognize these engine cases? Hint: these can be really fast ones.

Cheers/

Lasse

Two stroke trivia!!!! Ohh I love trivia, my guess would be a Honda rs125 due to how the head sits haha or were there other 125 gp bikes? Great detail on the build!

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