Modifying Motors

I own two 07 TTR230's and an 07 WFR450, and have changed the front sprockets from a 13 to a 14 on the 230's, and from a 13 to a 15 on the 450, (I tried 12, 13, 14, 15 & 16T spockets on the 450, and a 12, 13, 14 & 15T sprockets on the 230, with the best results as a 14T on the 230 and a 15T front sprocket on the 450). The rear sprockets are still the standard tooth count.:thumbsup:

The Xhaust spark arrestors were removed from all of the bikes, (a hacksaw being necessary on the 230's :bonk: ) ... and ... these bikes have been literally transformed! :applause:

The next step(s) are to remove all the airbox trumpets under the seat, along with the "fly screens" and a re-jet. I wondered if anyone had any ideas on jetting sizes for both the 230 and 450? :banghead: also;

How great, (or not?) is the 07 TTR 230 head? Would it benefit from a lil' porting, (or just mild polishing), (I've heard that they desperatly require removal of "dingleberries"), and/or an inlet valve size increase? :excuseme: also;

The local agent also suggested removing one of the head gaskets? ... Is there more than one head gasket? and;

Are there any better cams and/or pistons available for the 230's? :worthy:

Finally :blah: :blah: ... What is so great about all these aftermarket headers / pipes? and which one/s actually work? ... as against just making the bike sound faster by being louder! :ride:

Thanks "MuddyTTR" ... Every lil' bit helps :applause:

Sure thing.:thumbsup:

I own two 07 TTR230's and an 07 WFR450, and have changed the front sprockets from a 13 to a 14 on the 230's, and from a 13 to a 15 on the 450, (I tried 12, 13, 14, 15 & 16T spockets on the 450, and a 12, 13, 14 & 15T sprockets on the 230, with the best results as a 14T on the 230 and a 15T front sprocket on the 450). The rear sprockets are still the standard tooth count.:thumbsup:

The Xhaust spark arrestors were removed from all of the bikes, (a hacksaw being necessary on the 230's :bonk: ) ... and ... these bikes have been literally transformed! :applause:

The next step(s) are to remove all the airbox trumpets under the seat, along with the "fly screens" and a re-jet. I wondered if anyone had any ideas on jetting sizes for both the 230 and 450? :banghead: also;

How great, (or not?) is the 07 TTR 230 head? Would it benefit from a lil' porting, (or just mild polishing), (I've heard that they desperatly require removal of "dingleberries"), and/or an inlet valve size increase? :excuseme: also;

The local agent also suggested removing one of the head gaskets? ... Is there more than one head gasket? and;

Are there any better cams and/or pistons available for the 230's? :worthy:

Finally :blah: :blah: ... What is so great about all these aftermarket headers / pipes? and which one/s actually work? ... as against just making the bike sound faster by being louder! :ride:

hey i only 13 i dont no much bout this sort of stuff so dont bag me but, wat difference does it make to remove the air box trumpets and also wat difference does it make to remove the "fly screen"? thanks

i don't know about the 230, but the WR450 forum has an excellent index for jetting.

personally, i've had great success with the jd jetting kit. it is expensive, but worth the money.

check out the WR forum, and the 'performance index'. it's great.

To answer your question yamahajack_125 .... :bonk:

Stick some duct tape over your mouth and run around the block and time yourself :eek: then remove the duct tape, open your mouth, and repeat the exercise :prof: and post the results here :thumbsup:

Simply put ... More oxygen, (air in this case) = more power :applause:

Thanks kskyles :ride: ... I have followed some of the advice offered on the 450 forum, (and have made great headway) , (:banana: ), however I want to do more to the 230's :banghead: , as they are in my opinion the most amazing bikes.:applause:

I originally bought two of them, one for my son :thumbsup: and one for my girlfriend at the time :bonk: , however, as she has been traded in :censored: , I've started playing with it / them, and whilst they are now even more fun than before, (with a few mods) ... I want more!

To date I have gutted the silencer, and after sourcing a piece of pipe the same dia as the headers, and drilled a combination of 1, 2 and 3 mm holes through most of the length, welded that into the silencer cavity, surrounding it with fiberglass wool, using the original "end cap" with a larger opening to accomodate the new pipe :banana: It's much the same "loudness" as just removing the baffle/spark arrestor, :naughty: however they now have a lot more mid range as well as top end power :applause:

I've also removed the "flyscreen" , and ... as we tend to cross rivers fairly often, rather than cut open the side of the airbox ... I cut another opening on the top of the airbox and fitted a second "trumpet", (both of which have been shortened slightly) :D

What else ....

I've rejetted the bikes, (following the advice offered here), and I've ported them ever so slightly, (the stock heads are really poorly cast :foul: !), and I've profiled the rockers, (retarding the inlet and advancing the exhaust). also;

I raised the compression ratio slightly, by removing the centre of the head gasket and "replaced" it with gasket sealer, (yes, I re-used the old one ... It's an old trick we used in Formula Ford :thumbsup: )

i emailed engines only about the big bore kit for the 230 and they told me it was a substantial increase of low end power but it seems a little pricey. they need so compatition for the price to go down lol

No doubt about it ... increase cc's & you increase power ... particularly so in that you would then be going even more "over square" :banana:

Maybe the next step is to find a larger piston close enough to the 230's and take the plunge? ... bore it out an' see :bonk: ... the last time I did this meant manually going through a rather large stock room with a vernier in hand :crazy: (Anyone out there know which piston(s) have the same gudgeon pin diameter and same deck height, along with a larger dia?)

The exhaust valve is already on the large size, however a slightly larger inlet (+2mm), could be fairly easily accomodated :busted: , and logically ... a larger carb as well :thumbsup: .

The exhaust valve is already on the large size, however a slightly larger inlet (+2mm), could be fairly easily accomodated :busted: , and logically ... a larger carb as well :thumbsup: .

It sounds like you do alot of custom work. Instead of going to a larger intake valve (which may make power but will def. be pricey), why not experiment with 'necking down' and 'swirl polishing' the stock valve if you have access to a small lathe? I wouldn't think they'd be hollow or have any coatings that would get messed up (like the expensive bikes have). Maybe even pocket port the area directly behind it, including the guide protrusion area... this should increase airflow substantially through the inlet hole.

Hi Zer03230,

Yup I certainly do enjoy the challenge of squeezing every last nanowatt out of a motor :D

The advice you offer is sound, and I've already done it, (other than undercutting the valve!) ... and ... based on your input ... I take it you're also well versed in modding motors? :applause:

Anyhow ... back to the 230's ... I've also flow checked and tested the 230 heads ... they deeeeesperatly needed the mods! :cheers: and there were substantual increases there ... needed to rejet afterwards, which is always a good sign wrt increased flow and power ... had to go up another TWO sizes :eek:

Dunno what Yammie were thinking when they made the 230 head If I compare the workmanship to the 450 ... looks like they subcontracted the 230 to the Chinese :bonk:

As to valves, there is a South African :sa: company :thumbsup:http://www.steves.co.za/Performance_valves.html , that makes very reasonably priced valves that I've used before.

I must say that I prefer going larger, (within reason!), on inlets, and using a three angle seat :busted: as against undercutting / ditch cutting etc, which not only weakens the valve :thumbsdn: , but when you compare the additional area offered on the inside of a valve versus the outside, and the fact that a valve flows on it's periphery :thumbsup: .... nuf said :blah:

To date I'm up a little over 20% on the bottom end and only around 9% on the top, however I still have an unusual dent in the midrange????? where power seems to flatten off at 3000 to 3500 before beginning it's next accent. You can't feel it riding the bike, but it shows up clearly on a dyno ... probably timing? :excuseme:

Yes, I've built and modded many car and bike motors (even my bicycle get tons of carbon upgrades), and have always felt head mods are next after exhaust and intake upgrades to take advantage of the added flow capabilities. I have used undercutting on cars with big (2.11") valves before, and it has worked well, but yes, the 230's valves have much less material and would be much weaker when some is removed; I was just thinking it might be worth a try. Another trick I picked up on valve jobs is using a 5 angle instead of the standard three angle seat when you feel the turn is abnormally tight. I haven't had the head off my 230 yet, but I have a feeling it could benefit from this, as it helps create less turbulence in the chamber. BTW, how does the intake boot match up with the head? If it does not match up well, have you removed any material there?

As far as the dip in your power curve, it could easily be a number of things. Have you been changing needles or just main & pilot jets? The right needle is most important to a power curve; I'm working on a Duke right now at work that has an old aftermarket carb on it, which works well but is very hard to find parts for, and I have two only different needles but tons of mains and pilots to try out; each needle gives vastly different curves (one gives awesome top end, but is horribly lean in midrange/roll on, and the other rocks in the bottom, but sucks up top... both problems are helped with different jets, but gaps are created in the curve, and the right needle would solve this). Of course, the smallish intake vs large exhaust valves could also be causing this: the air rushes in at low rmps, giving good low end, and the exhaust is more than capable of evacuating at high rpms, giving good top, but in the midrange, neither valve nor the ratio between them is optimized to compliment each other and work well. A larger intake may drop your gains by 5% on bottom, but work more steadily through the mid to larger gains up top.

Thanks so much 0033230 for your input to date too ... it's much appreciated :worthy:

Way kewl on the Duke too :ride: I too own one, (a red 748R in rather wild trim ), :naughty: and it thankfully has fuel injection, which is soooo much easier to tune :p ...

Wrt the 230's tho' ... I'd like to say that the intake is all matched up pretty much the best it's gonna be with the standard lil' carb. and I'm reluctant to go and start experimenting with bigger carbs just yet, I'd rather look around for a larger piston that'll work, as clearly I'd then need a carb bigger than 28mm

On that score ... my local Yammie Mac suggested :blah: the XS650 SE piston as a possibilty??? ... need to confirm that with my vernier tho' ... it's a 75mm piston that'll raise the capacity to 256.3cc's , he also suggested a WR250 piston with a lil' machining??? ... and it's 77mm, which would raise the capacity to 270cc's:applause: .

On your carb suggestion, you're correct wrt partial throttle openings :thumbsup: , which lends me to thinking that my carb is probably set correctly, and that it may be ignition timing :cry: , on the basis that on the dyno it's "balls to the walls" full throttle, with engine RPM govered by the dyno loading ...

Tell ya what tho' ... I'll plug on an exhaust gas analyser and check it out at the "hiccup point" an' let you know :thinking:

Haven't managed to source a piston as yet, however I bolted on a WR250 Carb, (30mm Teikei y30p), with stock 250 jetting ... WOW!!! :applause:

The "dead spot" has gone, and this bike has come alive, to the extent that I think Yamaha may have purposely throttled the 230 with the lil Teikei 26mm carb to protect their 250 sales. :naughty:

Really?! That's interesting. Does it feel good everywhere? A big improvement? Will you be trying different jetting?

Haven't managed to source a piston as yet, however I bolted on a WR250 Carb, (30mm Teikei y30p), with stock 250 jetting ... WOW!!! :applause:

That'd be the TT-R 250 carb. The WR 250f carb has a 37mm Keihin FCR carb

Hmmmm ... Good kwessie on where the carb comes from? ... Dunno? as I don't own a WR or TT250 :worthy:

Our local Yammie agent sold it to me as a WR250 carb? :bonk:

It is a 30mm Teikei y30p tho' :thumbsup: and I haven't done anything other than setting the idle ... CO's look fine, the "minor" flat spot dissapeared and top end is definetly up, which means 0033230's advice wrt the "flat spot" being fuel mixture was spot on :)

That's awesome; glad to hear the bigger carb works so well. I wonder if a 32mm Keihien carb from a KLR250 would work as well? I think there is one in the box of carbs at my work... might be worth a try.

Now that would be an interesting test :applause: , as the reading I've been doing lately suggests that modern bikes benefit from carbs larger than "old school thinking", (ie. approaching 95% as against 80%), without bottom end losses and top end flat spots? :worthy: ... certainly makes sense when I see standard inlet valves around the 85% mark? ...

I just wonder how efficiently the venturi would work with only a 5% reduction in dia?:crazy:

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