Tw250 Six Speed
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ronnydog
81 - 96 of 96 Posts
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The engine swap topic has been done to death. The only way to know what's possible is to do your own homework, decide if all the downsides and fabricating hassles are within your budget and skillsets, then do like Ronny, get greasey and take one for the team.
As far as successful, completed and rideable swaps I know of only two. One is a streetified water pumper swap owned by one of our own members and the other done by a guy on a French TW site who managed to stuff an XT250 into one with a lot of frame work and an offset front downtube. Aside from those I know of no other functional swaps ever seeing completion. Most have stuck to modifying the existing motor with parts from the aftermarket or within this engine family, which include the TTR225, TTR230, XT225, Beartracker and Timberwolf quads and the TriMoto three-wheelers. The Reader's Digest version is that anything possible within the engine family also applies to the TW motor. All the heads and valve sizes are essentially the same within this engine family and the valve seats are too close together to allow more than a mm of increase. The placement of the cylinder studs and wall thicknesses limit the size of overbores, but duplicating XT250 numbers is possible. The longer stroke cranks, charging systems, clutches and kickstarter assemblies from the 225's can be swapped freely or modified to fit, and all the cylinders will fit TW cases with case mouth enlargement. Aftermarket pistons exist in fairly conservative sizes, and Webcam makes a few cam profiles, but all use stock lobe centers. A couple of XT guys have built strokers using offset crank pins, but as far as I know Ronny's the first to use a properly redrilled crank. Macbig has done a number of builds of builds in various overbores and configurations and has dyno charts on those.
That oughtta get you up to speed.
As far as successful, completed and rideable swaps I know of only two. One is a streetified water pumper swap owned by one of our own members and the other done by a guy on a French TW site who managed to stuff an XT250 into one with a lot of frame work and an offset front downtube. Aside from those I know of no other functional swaps ever seeing completion. Most have stuck to modifying the existing motor with parts from the aftermarket or within this engine family, which include the TTR225, TTR230, XT225, Beartracker and Timberwolf quads and the TriMoto three-wheelers. The Reader's Digest version is that anything possible within the engine family also applies to the TW motor. All the heads and valve sizes are essentially the same within this engine family and the valve seats are too close together to allow more than a mm of increase. The placement of the cylinder studs and wall thicknesses limit the size of overbores, but duplicating XT250 numbers is possible. The longer stroke cranks, charging systems, clutches and kickstarter assemblies from the 225's can be swapped freely or modified to fit, and all the cylinders will fit TW cases with case mouth enlargement. Aftermarket pistons exist in fairly conservative sizes, and Webcam makes a few cam profiles, but all use stock lobe centers. A couple of XT guys have built strokers using offset crank pins, but as far as I know Ronny's the first to use a properly redrilled crank. Macbig has done a number of builds of builds in various overbores and configurations and has dyno charts on those.
That oughtta get you up to speed.
Joined
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1,446 Posts
Updates...... I need to still figure out the carb. I'm looking at a 2011 Yamaha Raptor 250 Carb Carburetor for the build. It's not very tall and my use the same cable. I have lost some of my momentum for now with the loss of my good friend Russ. We talked this build into what it came to be and without him and his input ....well....... I need to find an other partner with much more tec knowledge than I have to help with it! My efforts have been in the Two Wheel Tank Trailer build to have it ready for deer season and for a archery elk hunt in AZ. I ordered a Jet Sled to use instead of the action packers to carry Elk quarters. I will finish the 250 build and can see me working on it later this year. Thanks for asking
Ronnydog
Ronnydog
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7,044 Posts
In response to the questions in email about Tdub2:
Tdub2 uses all the XT225 trans, shifter, clutch, crank, etc., with the only non-XT parts in the bottom end being the TW countershaft turned to match the XT profile, the TW left side cover, flywheel, and electrical coils, the TW balancer, the TW oil pump, the TW kick starter lever, and the TW cases bored to fit the over-size liner. The XT crank was welded and redrilled, uses a Suzuki connecting rod and a Honda piston with the valve reliefs ground to clear and some of the skirt ground off. Doing a 6-speed, 5-disc clutch, and kick start really isn't that big a deal--other than the countershaft, it's a bolt-in. Doing 267cc is a heck of a lot more work, don't ask what the rod and piston came from, I picked them out of a pile at a wrecker and he ordered matching new replacements for me. A 250cc TW is easy--just use a XT225 or TT-R 225 or 230 crank and a religned cylinder in a bored case, and it's pretty much a bolt-on using xr100.com parts. Oh, and money. Lots and lots of money. I have over $7k in Tdub2 just in parts, not counting the cost of the bike, and all the welding and machine work was free since I have access to a tool and die shop loaded with the latest and greatest CAD-CAM and CNC toys, and the ability to maintain tolerances down to hundred thousandths of an inch, close enough a 1*F change in temperature causes enough thermal expansion or contraction to measure the change. Such equipment isn't really necessary, but it sure makes it easier. How many $1/2milllion machines do you have access to? I also have 49 years experience building performance engines and drivelines ranging from go-karts to world champion pulling trucks to Ascot trackers to unlimited hydroplanes. Even my airplane is powered by an automotive engine converted to FAA certifications.
No, there is no Tdub2 write up and there never will be. If you lack the tools and skills, you don't need to be taking on a project like this unless you have a mentor at your elbow with the skills and tools. Same goes for the EFI--if you can't do the R&D, don't try or you'll only be frustrated. And if you think a 6-speed TW267 is complicated, try a Honda SOHC CB712 with EFI and electronic ignition conversion.
I'm only making this post because there are good people on this site with the skills and the hearts of good teachers willing to mentor and make these dreams come true. If you really want to get in to such mods, by all means find a mentor, break out the wallet, and get started on a very long and expensive but ultimately supremely rewarding learning curve. Best to buy a 2nd bike, because your hotrod will be down for a looooooong time.
Projects such as these take hundreds of hours of research, planning, and wrenching, and a description of the entire process would overwhelm a website. Then 3 relative newbies would gang up on the contributor like a bunch of punks on a playground and bombard with snarky comments because obviously the person who redesigned, rebuilt, and rides these one-offs every day has it all wrong.
Back to minding my own ... .
Tdub2 uses all the XT225 trans, shifter, clutch, crank, etc., with the only non-XT parts in the bottom end being the TW countershaft turned to match the XT profile, the TW left side cover, flywheel, and electrical coils, the TW balancer, the TW oil pump, the TW kick starter lever, and the TW cases bored to fit the over-size liner. The XT crank was welded and redrilled, uses a Suzuki connecting rod and a Honda piston with the valve reliefs ground to clear and some of the skirt ground off. Doing a 6-speed, 5-disc clutch, and kick start really isn't that big a deal--other than the countershaft, it's a bolt-in. Doing 267cc is a heck of a lot more work, don't ask what the rod and piston came from, I picked them out of a pile at a wrecker and he ordered matching new replacements for me. A 250cc TW is easy--just use a XT225 or TT-R 225 or 230 crank and a religned cylinder in a bored case, and it's pretty much a bolt-on using xr100.com parts. Oh, and money. Lots and lots of money. I have over $7k in Tdub2 just in parts, not counting the cost of the bike, and all the welding and machine work was free since I have access to a tool and die shop loaded with the latest and greatest CAD-CAM and CNC toys, and the ability to maintain tolerances down to hundred thousandths of an inch, close enough a 1*F change in temperature causes enough thermal expansion or contraction to measure the change. Such equipment isn't really necessary, but it sure makes it easier. How many $1/2milllion machines do you have access to? I also have 49 years experience building performance engines and drivelines ranging from go-karts to world champion pulling trucks to Ascot trackers to unlimited hydroplanes. Even my airplane is powered by an automotive engine converted to FAA certifications.
No, there is no Tdub2 write up and there never will be. If you lack the tools and skills, you don't need to be taking on a project like this unless you have a mentor at your elbow with the skills and tools. Same goes for the EFI--if you can't do the R&D, don't try or you'll only be frustrated. And if you think a 6-speed TW267 is complicated, try a Honda SOHC CB712 with EFI and electronic ignition conversion.
I'm only making this post because there are good people on this site with the skills and the hearts of good teachers willing to mentor and make these dreams come true. If you really want to get in to such mods, by all means find a mentor, break out the wallet, and get started on a very long and expensive but ultimately supremely rewarding learning curve. Best to buy a 2nd bike, because your hotrod will be down for a looooooong time.
Projects such as these take hundreds of hours of research, planning, and wrenching, and a description of the entire process would overwhelm a website. Then 3 relative newbies would gang up on the contributor like a bunch of punks on a playground and bombard with snarky comments because obviously the person who redesigned, rebuilt, and rides these one-offs every day has it all wrong.
Back to minding my own ... .
2003 TW;2018 KLX250 camo ; former owner of 2006 TW (retired at 23k); 19' S3, 09' F-250, 97' Cherokee
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607 Posts
QWERTY,
Your reply started awesome; it was informative, detailed, and quite well-worded. The end though...golly, it got kind of negative. This is not rocket science. You're right about the money though, I can agree there. I think the rest comes down to ambition and time. The more a person has access to tools and fine machinery is great, if not, you'll just pay more.
Can we not stamp out people's flames here? Sure a bit of a wind guard is fine, but a smothering?
I do appreciate your knowledge, experience and realistic views. I don't appreciate the negative nancy.
Your reply started awesome; it was informative, detailed, and quite well-worded. The end though...golly, it got kind of negative. This is not rocket science. You're right about the money though, I can agree there. I think the rest comes down to ambition and time. The more a person has access to tools and fine machinery is great, if not, you'll just pay more.
Can we not stamp out people's flames here? Sure a bit of a wind guard is fine, but a smothering?
I do appreciate your knowledge, experience and realistic views. I don't appreciate the negative nancy.
Joined
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1,446 Posts
I have built three TW 225, one TW 250 six speed and starting to build another TW 225 six speed on a small bench in a condo. The only other motorcycle motor I have built was back in the 70s, a honda 90 built to 138. It's not hard to do if you can read the service manual, buy a few needed tools, make a couple phone calls, read the post and fallow what those of us have done already. When I built the first motor I tried to use all the TW parts I could so others could do the same thing without buying a TTR or a XT225 motor. All of those who like stock bikes good for you, those of you who want more out of your bike I'm here to help if needed. I could not climb the hills, carry the loads or pass traffic as easily without the extra CCs. It's about having fun and what's more fun than twisting the throttle and the TW speeds up in 6th gear instead of just hearing more noise?
Ronnydog
Ronnydog
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7,044 Posts
I don't give a damn what you appreciate or don't appreciate. The tone of your post with its backhandedness is exactly why I don't waste much time with this site any more. Too many people with the same level of non-experience and the same condescending and judgmental attitude. It has nothing to do with Off-Topic as so many whiners whine.
Summary for those who really want to give it a go:
1) 6-speed and 5-disc clutch is bolt-in for 200cc+ cranks, other than turning the TW countershaft, won't work with the 125 due to different primary drive sprockets;
2) 225-230cc is bolt-in other than opening the cylinder hole in the top case;
3) 250 is bolt-in using xr100.com parts and services other than opening the cylinder hole in the top case;
4) 6-speed works great with any displacement. The closer gaps between gears make the bike much better for highway speeds, even with a stock engine, because shifting 5th top 6th doesn't drop the engine right off the torque curve like shifting the stock trans from 4th to 5th. Sweet! Sweet! Sweet!
Any person who can read and follow instructions can build those three. Ronnydog is right, combine a 6-speed with a 225 to 250cc engine on an XT/TT-R crank with a few moderate tweeks for midrange torque and you'll have the TW Yamaha should build.
A 250 on the stock 225/230 stroke is pushing the practical limit for bore as thinner walls will result in odd flex patterns due to thermodynamic expansion and contraction which would likely cause a plethora of reliability issues. The only other option is stroke. Actually building a stroker crank and engineering and machining the cylinder spacer to clear the pistons skirt while providing for functioning cam chain guidance and tensioning while maintaining a practical compression ratio is a totally different animal. As far as I know only Sebastian and I have actual running stroker TWs, though they are no more difficult than stroker XTs and TT-Rs, and there are several of them running around.
Just do it.
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264 Posts
^ my upcoming project is getting nearer^
I just want to thank everyone who has contributed to this thread. There has been a lot of research done by some willing members to get to the point where we are now of having access to all of this knowledge.
I have searched all all the threads that I could find covering this subject before starting my project.
Thanks to others hard work and trial and error, I have figured out what I need. I think I have acquired all of the pieces to convert my TW to a six speed. I have the transmission parts, clutch, and side cover from a TTR225. I have had an output shaft machined to accept the new gear set and I have added a hole to the side case to accept the TW kickstarter. I will keep the stock displacement.
I hope to install all of the parts after the riding season when things slow down for me. I will give an update afterwards to give my thoughts on the conversion.
Thanks again to all of you that have done the conversion and have been willing to share your knowledge, you know who you are.
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1,446 Posts
Leben, good for you! It will make your TW feel like it weighs 150 lbs and the extra gear will help keep it in the power band. It took me a some time to get used to the extra gear. I'm starting a 225 six speed this month with a Wiseco piston.
Ronnydog
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21,980 Posts
Still want you to build me up a 250cc stroker / 6 speed Ronny.... 
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1,446 Posts
Still want you to build me up a 250cc stroker / 6 speed Ronny....
ENGINES ONLY The Performance Specialists since 1990 would be your best choice for now on a 250cc.
Ronnydog
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21,980 Posts
bored and stroked 250 six speed, wonder how much they would charge? I didn't see any TW engines listed? We got to get you a bigger table to work on in the condo....
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1,446 Posts
bored and stroked 250 six speed, wonder how much they would charge? I didn't see any TW engines listed? We got to get you a bigger table to work on in the condo....
It can be done the TTR motor is almost the same as the TW. I have talked to him in the past and he is very knowledgable motor builder. It would be good to know what he would charge for a TW250 build? I will call him next week and let you know.
Ronnydog
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3,813 Posts
talk about my neighborhood... that's about 10 minutes from my house. hmmmm.... talk about trouble, just might have to ride over there next week.
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