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Thread: Curiosity regarding 250cc / 6 speed conversions

  1. #11
    Senior Member lbxr's Avatar
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    I have built 2 six speed/229cc conversions using a 71mm bore, if I recall correctly....All off the shelf jugs and pistons. IE cheap! These have been proven to be very reliable for the last 2 years or so. With the type of riding we do here, lots of first and second gear slow sustained uphill climbs with alot of high throttle settings, I am already running into overheating issues at 229cc....And we generally have mild cool conditions here. We seldom ride much if it is over about 80 degrees here... Makes me wonder if engine has the ability to shed enough heat at 250 cc? I kinda feel we are right at the limit at 229cc for our conditions here. My gut instinct is that 250cc may be a long climb for a short slide.... on the other side of the equation, I think weight reduction makes an even bigger gain for the TW. Mine is down about 35lbs or so and this makes a huge difference off road.

    My point is not to discourage you on this, but rather to consider the well beaten path at about 225cc....IMO a real nice sweet spot for these motors! And cheap too!
    Willys714 likes this.

  2. #12
    Senior Member vanillagorilla1's Avatar
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    im curious to hear about the heat issue. mine is 225 or 70mm bore with the 10.25:1 cr. Ive ridden multiple trips of over 300 miles in a day in temps above 90. lots of WOT on the highway and gravel roads. I use an oil cooler and a trail tech voyager to keep a watch on temp. cylinder head temps usually 300-350 and never ever breaches 400 which I understand to be dangerous. I might add that I ride all year around unless there is snow or ice. Temps range from 20 to 100 and elevation of 800 to 7000 or so. anything above 5000 it starts to blubber in the mid range. I suspect that I have a richer jetting set up that you. It might help that Im 125# as well.
    93 tw. running like clockwork
    225 6 speed complete!
    82 honda gl500 silver wing. sold to a new home 11-24-17
    03 ducati monster 800sie. full rebuild and a danger to the public Hidden Content for sale

  3. #13
    Senior Member lbxr's Avatar
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    Quote Originally Posted by vanillagorilla1 View Post
    im curious to hear about the heat issue. mine is 225 or 70mm bore with the 10.25:1 cr. Ive ridden multiple trips of over 300 miles in a day in temps above 90. lots of WOT on the highway and gravel roads. I use an oil cooler and a trail tech voyager to keep a watch on temp. cylinder head temps usually 300-350 and never ever breaches 400 which I understand to be dangerous. I might add that I ride all year around unless there is snow or ice. Temps range from 20 to 100 and elevation of 800 to 7000 or so. anything above 5000 it starts to blubber in the mid range. I suspect that I have a richer jetting set up that you. It might help that Im 125# as well.
    I am using the Wiseco 10.25/1 piston as well. Also premium fuel. Our climbs often start at sea level and climb to 1500 to 2000 feet or so, all single track with a few technical sections that require full throttle in second gear to make it....Seldom any higher than 2nd gear and a quite a bit of first gear work as well. All pretty slow and somewhat technical. The bikes get hot! I will get some pinging when it is hot, especially if I lug down to low in the RPM band and have the throttle open some to try and regain momentum....this is what I am basing the overheating on. We also ride on the beach where it is much cooler and breezy with deep sand. We do alot of hopping over logs and such and lug the engines just as hard in first and second gear as we do in the hills....The bikes are much cooler and do not ping at all and some of the sandy stuff is wide open throttle in 2nd gear with lots of lugging...
    joeband likes this.

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  5. #14
    Senior Member vanillagorilla1's Avatar
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    that makes sense. Ive had it approach the 400 mark a few times on WOT steep hills in first. I have yet to find a hill long enough at low speed to be an issue. Ive had a couple times where it would ping when lugging when It was hot but it subsided quickly. Ive never had to shut it down from heat. I always run premium fuel as well. Im hoping dropping the CR to 9.5:1 will help curb the heat a little and keep it from pinging. I am building the 250 as a complete and if it proves to be less reliable the 225 will go back in. I realize im pushing the limit further, but after a few conversations with frank and his kit thats 11.5:1 that he gets almost 30hp out of I think im well in the safe limit. he swears he runs just premium pump gas. I remember talking with you in moab a couple years ago and comparing notes. seems like out engines were close twins.....
    joeband and lbxr like this.
    93 tw. running like clockwork
    225 6 speed complete!
    82 honda gl500 silver wing. sold to a new home 11-24-17
    03 ducati monster 800sie. full rebuild and a danger to the public Hidden Content for sale

  6. #15
    Senior Member Spawner's Avatar
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    Quote Originally Posted by vanillagorilla1 View Post
    Im gonna take a whack at answering your questions bases on current and growing knowledge. Also you mention you're looking at a moto4 225 head and mention head in your first list and because of wording I think you mean cylinder. Also to state my marginal credibility I do have a current 225 6 speed with 15k or so on it now and a 250 on the bench in the works. I have a thread currently going as I make progress. So........ the la sleeve 5679 will not drop into any cylinder you choose. It has a larger OD than the 225 cylinder sleeves by a fair bit. The height is almost spot on so Im not thinking it will need to be trimmed. The one issue I see is that the lip at the top is also a fair bit larger and will be over the holes that the dowel pins go into. When I spoke with LA sleeve last week they said they prefer to let that happen and rebore the dowel holes. The piston will never be the perfect fit when you're doing this. Sleeves come undersized a bit and don't have an internal surface finish until they are done. This is because pistons vary slightly and once installed into a cylinder things can distort slightly. So the process goes remove old sleeve, machine bare aluminum cylinder to fit new sleeve, install new sleeve, FINISH BORE AND HONE SLEEVE TO PISTON SPECS. I don't see at this time a larger oversize piston for future bores and personally don't care to much about that. Now also understand that you're going to have to machine the case mouth as the new sleeve is also larger than any 225 sleeve. Ive had this done before multiple times and its no big deal. you already know about the output shaft, left cover ect. Fair warning my current ttr225 cases 01 model I believe didnt come bored for a kicker. I had it done and its possible but your 04 cases may not either. By this I mean the right cover AND the actual right side case. I am waiting for a piston and crank pin and things are all headed off for final work. I am having LA sleeve machine and install the ya5679, ken occonor is rebuilding my crank shaft, case machining done local by a friend for beer, some one in California (twbrians recommendation) machined the output shaft, and I will do all the wrenching. LA sleeve quoted me 250 for the sleeve itself and all of the machine work to install it and ill tell you that's more than fair. Do yourself a favor and send it to the place that makes the sleeves and does it all day every day. Now a closing statement then Ill include some pics past and present....... Your TW will never be fast and this isn't cheap. If you want significantly more power buy something else that has more power and better chassis/brakes/suspension. I spent over 1000 bucks last time on the 225 and that's what i'm doing again on the 250. If you're brave and like to play press forward as it is a fun process, but be prepared to shell out and don't cut corners. Unless you know the condition I would (and did) replace all bottom end bearings, valves, valve springs, all seals and gaskets, cam chain guides, cam chain, and have the crank rebuilt (crank pin, con rod, big end bearing). I will be keeping a good thread on the 250 as I go since theres not as much info on it. Good luck

    ttr225 cylinder with sleeve removed
    Untitled by dolphaxel, on Flickr
    heres where the kicker goes and you can see its not machined
    Untitled by dolphaxel, on Flickr
    after I did the machining
    Untitled by dolphaxel, on Flickr

    This is going to be a slow over the winter project for me, just to see if I can do it. I am going to attempt to do all the machining myself to save money. Even if it seems like cutting corners, its the learning (curve) I'm after. I've never really done much engine work, so this should be a neat project. Its nice to start with a general knowledge of compatible parts, so I can pick up used deals along the way. Thank you all for contributing, I recognize some of you from the many threads I've been reading. And yes, I did mean cylinder...

  7. #16
    Senior Member joeband's Avatar
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    just my short $.02:

    my motor tw226 6spd is a rebuilt 2003 ttr225. when i bought the motor off of craigslist (the guy pulled it out of a dumpster, he told me after i bought it!) already had one oversized bore and piston installed. it uses the tw left side cover and tw output shaft, the xtra work to get to 250 i can't speak to, but these three observations still hold.

    1. the machining gentleman TW-brian i and used to cut the other groove for the 6th gear in the tw output shaft was in washington, though last i heard he wasn't doing more. was around $100.
    if i had to say which aspect was better result of this swap, the extra power or the extra gear... it would be close, but i think 6th spd wins.

    2. i too used the ttr225 right side cover and had the kicker hole bored out. works great, never leaked, totally worth it.

    3. it wasn't cheap, but i've never regretted it.

    good luck with you build.
    Last edited by joeband; 04-16-2018 at 06:48 AM.
    Spawner likes this.
    1994 TW226- 6spd. 10w-40 synthetic, XTHidden Content , XT225 stainless header, +2" Joemama swingarm, lizrd cooler, +20% fork springs, +25% rear spring, 2001 speedo w/ trip odo, pro taper atv bars, bark busters, shinko 241 front tire, front fender w/ mr bracket bracket, Hidden Content , o-ring chain, ricochet skid plate, Hidden Content , XT225 rear brake cam lever, folding-tip shifter, cycle rack, kolpin 1.5 aux tank & 1450 pelican case. Hidden Content or Hidden Content

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  8. #17
    Senior Member vanillagorilla1's Avatar
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    Quote Originally Posted by joeband View Post
    just my short $.02:

    my motor tw226 6spd is a rebuilt 2003 ttr225. when i bought the motor off of craigslist (the guy pulled it out of a dumpster, he told me after i bought it!) already had one oversized bore and piston installed. it uses the tw left side cover and tw output shaft, the xtra work to get to 250 i can't speak to, but these three observations still hold.

    1. the machining gentleman TW-brian i and used to cut the other groove for the 6th gear in the tw output shaft was in washington, though last i heard he wasn't doing more. was around $100.
    if i had to say which aspect was better result of this swap, the extra power or the extra gear... it would be close, but i think 6th spd wins.

    2. i too used the ttr225 right side cover and had the kicker hole bored out. works great, never leaked, totally worth it.

    3. it wasn't cheap, but i've never regretted it.

    good luck with you build.
    for my personal curiosity did you have to machine the right case half as well? I know you bored the side cover and I assume the bore where you press the seal into, but on my 2001 cases Yamaha didn't even finish up the case to accept the kicker shaft as seen in my photos. Reason I ask is I haven't heard of anyone else having to do this and I was trying to figure out a pattern as to what years were left unmachined.
    93 tw. running like clockwork
    225 6 speed complete!
    82 honda gl500 silver wing. sold to a new home 11-24-17
    03 ducati monster 800sie. full rebuild and a danger to the public Hidden Content for sale

  9. #18
    Senior Member TW-Brian's Avatar
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    Quote Originally Posted by vanillagorilla1 View Post
    for my personal curiosity did you have to machine the right case half as well? I know you bored the side cover and I assume the bore where you press the seal into, but on my 2001 cases Yamaha didn't even finish up the case to accept the kicker shaft as seen in my photos. Reason I ask is I haven't heard of anyone else having to do this and I was trying to figure out a pattern as to what years were left unmachined.
    My 2000 TTR225 engine case was already machined to accept the kickstarter shaft assembly .

  10. #19
    Senior Member Spawner's Avatar
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    Upon looking at generator/stator fiches, it doesn't look like there is a tw200 stator that will plug into the ttr wiring harness. what am I missing here?

  11. #20
    Senior Member vanillagorilla1's Avatar
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    Quote Originally Posted by TW-Brian View Post
    My 2000 TTR225 engine case was already machined to accept the kickstarter shaft assembly .
    what the hell did I get a friday afternoon case or what!?

    Quote Originally Posted by Spawner View Post
    Upon looking at generator/stator fiches, it doesn't look like there is a tw200 stator that will plug into the ttr wiring harness. what am I missing here?
    You use the 200 fly wheel and the 200 stator and pickups stay with the tw left case. you will have no ttr electrics at all.
    93 tw. running like clockwork
    225 6 speed complete!
    82 honda gl500 silver wing. sold to a new home 11-24-17
    03 ducati monster 800sie. full rebuild and a danger to the public Hidden Content for sale

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