1981 250R resto-mod

[81300R]

Wanted to start a build thread on my project.

I picked this bike up in tucson AZ. Was told it had a rebuilt 300. They tried to use a polaris piston in it, which was the wrong compression height. Needless to say it didnt run right.

I decided to take the motor down and have the crank rebuilt. I did quite a bit of research and found a shop out in California that had a 300R Wossner 77mm piston, the only one left from a batch they had made. The 300 has some mild port work, and (the only one ive ever seen) a S&S Headers expansion chamber.

After pulling the motor i stripped it to the frame and gave it a fresh coat of red. I cut the swinger apart and stretched it 3”.

New seat cover, new plastic, PWK38.

Planning to powdercoat much of the parts. Not going for show, but a nice rider. Trying to recreate an early race bike. I love the look of the Selvy 250R.

https://i.ibb.co/G2PgHWR/C25957-B5-61-DF-45-AA-963-F-43-FDB3-AAC502.jpg (https://ibb.co/r6yndxH)
https://i.ibb.co/qD9PbFk/804470-FF-1-C8-D-4186-A358-0284-B61-BC5-A3.jpg (https://ibb.co/QJn1sjr)
https://i.ibb.co/b2N65Qh/D4596-B46-F118-4-B71-A8-FE-71965-DED7-D98.jpg (https://ibb.co/4Y4FRKy)
https://i.ibb.co/17FkDyz/F8-A7-E722-0-E40-492-A-AAEF-28-F94757-C2-B0.jpg (https://ibb.co/RYRqxrj)
https://i.ibb.co/7Kbx6MP/6-C4-E169-E-88-CB-444-D-B9-AC-42-A322-E5-FDFD.jpg (https://ibb.co/6FNcf9z)

[81300R]

https://i.ibb.co/5Bxf0Q7/C3-BC6-EEF-A6-A5-4748-85-E3-D9-AEFF11-E50-A.jpg (https://ibb.co/syJMfTB)
https://i.ibb.co/d0pT7q7/560-C7718-0-C5-F-4352-AD75-9-C5-CA7-B7-E4-A4.jpg (https://ibb.co/WWzhsws)

[81300R]

Played around with some powder. Ive got Candy gold coming for the swinger and triples.

One of the best tools ive purchased has been a Redline powdercoating gun!!

https://i.ibb.co/L5YQgDr/716-AF606-79-D7-4-BB1-9215-44-B1-A05-D9106.jpg (https://ibb.co/VmJHC0x)
https://i.ibb.co/7tjYHqz/B57-D0522-B67-C-43-A9-9500-3492-A38270-EB.jpg (https://ibb.co/F4mx9FW)
https://i.ibb.co/1MMNVR4/889-DB367-2560-4-C98-9-C8-B-1-C4188-F9762-A.jpg (https://ibb.co/vhhW5LM)
https://i.ibb.co/wpMS33W/03-F075-EE-A04-E-4-B62-AEC5-469-D2408-trailprotrailpro-CB.jpg (https://ibb.co/NWZ9QQj)
https://i.ibb.co/FJwcNPV/C79792-EB-D35-A-4254-B934-49-E56-F255-F52.jpg (https://ibb.co/6bPGVdB)

[Footy]

Looks good! First time I have ever seen a supertrapp on a 2 stroke.

[81300R]

Looks good! First time I have ever seen a supertrapp on a 2 stroke.

Thanks, it was something i had on the shelf for an XT600 i used to own.

Blasted and put the base coat of chrome on the swinger and triples.

https://i.ibb.co/5R4Rzhp/1407-AED7-8-CE6-47-B7-84-D7-F27-C1-E0444-D3.jpg (https://ibb.co/KrhrQx4)
https://i.ibb.co/tDHmTJD/2-F33-FBF8-F296-445-F-86-D3-3-A8-DD03-DB30-A.jpg (https://ibb.co/BBfz5CB)

[81300R]

It was pretty difficult to get an even coating of the translucent candy gold. Had to go pretty thick. Came out ok i think.

https://i.ibb.co/8sRSTXf/F8923-AE1-6-EC5-4-B05-8-BDD-0291-F0-E37-F77.jpg (https://ibb.co/mTYM1S2)
https://i.ibb.co/fY8YKWf/6-BF904-E8-FEDB-41-DD-BE10-D0-FAA3-EFA0-D7.jpg (https://ibb.co/4ZsZDLz)
https://i.ibb.co/mBYYsFf/8-C8-E44-A2-68-F1-4-A49-95-B8-8853-A2-AC172-E.jpg (https://ibb.co/cvpp5X4)
https://i.ibb.co/pnLJwm9/09843-EC2-8-D00-4-E8-F-869-B-7-F37-BBCB6-C4-E.jpg (https://ibb.co/d75GMhz)

[81300R]

Fitting some parts while i wait to get my crank and 300 cylinder back from the machine shop.

https://i.ibb.co/txSbWv4/CFB5-F296-0-B8-F-402-D-B041-C36390-F2-B942.jpg (https://ibb.co/VQdvPzt)
https://i.ibb.co/sJJPKqD/D501989-E-A1-C9-465-B-86-F7-90-AB7-D458697.jpg (https://ibb.co/cXXv6Qp)

[sjsst41]

Looks good ! It’s amazing how much time goes into these projects when you have to do something to each & every part, but satisfying when it all starts to come together.

[81300R]

Looks good ! It’s amazing how much time goes into these projects when you have to do something to each & every part, but satisfying when it all starts to come together.

I wasn’t planning on going quite this deep but every thing i took apart was trashed :lol:


The shock was leaking a bit of oil around the bladder, cleaned it up and with a bit of grease around the sealing surface it held a nitrogen charge again, until the hose blew. Substituted a 10,000 psi rated grease gun whip for that.

Forks stripped down for seals, of course all the teflons are trashed as well. Wheel bearings shot. Brakes missing. Polaris piston in a worn out 76.5 bore. Crank bearings toast. List goes on!

[81300R]

Found that a sprocket for a XL175 uses the same bolt pattern. JT sells a 38T under 30 bucks.

Put the brake together.

https://i.ibb.co/VqfQJrj/A92-EE8-DF-691-E-4-C86-844-B-2478589-D9-AF0.jpg (https://ibb.co/0GHFm8D)
https://i.ibb.co/mz2FS6x/135-ABF3-E-B9-BC-4-A53-8-E74-744-D51-F5-D8-A4.jpg (https://ibb.co/vzTvDZt)

[81300R]

Repaired a few cracks in the front wheel, mounted the sprocket and shock reservoir, and got the bottom end put together.

https://i.ibb.co/0X4nWZs/379-B4943-F2-A6-432-D-8577-AAC98-EEA9-D29.jpg (https://ibb.co/vBycrmX)
https://i.ibb.co/6JNCYFg/369-B02-C9-7848-4969-trailprotrailpro-F5-30449594-CF5-B.jpg (https://ibb.co/4gJrWpP)
https://i.ibb.co/C2xx0KL/DF75-CDC6-59-C2-4-BBE-B39-C-9-F328380102-C.jpg (https://ibb.co/q5bb1Y6)

[atc300r]

Man I'm loving this build.

[81300R]

Rebuilt the forks and port matched the intake and exhaust adapters.

Had some major issues with the paint i used. Taking way too long to dry. Giving it some heat..

https://i.ibb.co/t8Bghsv/8-A63-E1-B1-948-B-48-F5-869-B-F0808-B242-E79.jpg (https://ibb.co/18Z1nqP)
https://i.ibb.co/QDfYDx2/4-CF3-ADF1-541-A-4-F49-89-A2-FA07-C7-AB5-D78.jpg (https://ibb.co/7kXrk0w)
https://i.ibb.co/hdhsQLT/D620-FE5-C-1-AC2-4768-8420-7-BD8363-E1-E22.jpg (https://ibb.co/my1JZbP)
https://i.ibb.co/mBTm4h0/A4-F25-E64-22-trailprotrailpro-4061-953-E-773-CE0450-BD6.jpg (https://ibb.co/6Zw2FD8)
https://i.ibb.co/dLbw5Nn/B5414-A37-6999-4-A62-BF58-1442035-A0668.jpg (https://ibb.co/7Rgd137)
https://i.ibb.co/fCY13Xh/3-E9191-DE-1-AAB-45-A3-BC65-31-C4-CBD18216.jpg (https://ibb.co/8jDKymW)
not me images (https://imgbb.com/)

[81300R]

Paint is finally setting….Bottom end in. Top end on. Single shim out of a FL350 headgasket for a bit more compression. A bit more port matching to do on the intake. Paint fish eyed on the head so ill have to redo that.

Fun seeing it come back together.

https://i.ibb.co/WxhyjbS/D9-A8-E4-F1-C7-A0-4-C03-9828-F6-CB6-BE6-E1-C0.jpg (https://ibb.co/qySsVtb)
https://i.ibb.co/MCVPyhM/200-DBC79-616-C-4448-AB98-0-E078-DD4-B634.jpg (https://ibb.co/vjPLCBZ)
https://i.ibb.co/txr8928/24-BFA5-A7-D586-482-E-B610-D2-DD8-CC27-BD7.jpg (https://ibb.co/9V5s74s)
https://i.ibb.co/FHwQJ8n/A62-C60-B3-E021-4165-9-AE7-5084-E6-A876-F4.jpg (https://ibb.co/BnZhjTw)
https://i.ibb.co/J7pFyKZ/2052-F0-C7-B0-C1-44-F9-ABF0-9-C9022-B1-D85-F.jpg (https://ibb.co/9T43VNP)

[81300R]

Got it fired up. Funny enough it still isn’t running properly. Sounds like a rev limiter past 1/4 or so throttle. I assume a CDI issue. If anyone has one i could try it would be greatly appreciated!

https://i.ibb.co/Rb4XV1q/196-CE3-F1-62-D2-4-D2-F-9084-CCD4-E09-FCF43.jpg (https://ibb.co/tKP0WS9)
https://i.ibb.co/grQnN53/3743-FE85-4087-43-F9-975-A-7-E7-B1-E8506-F5.jpg (https://ibb.co/XW6w1hb)

[350for350]

That almost makes me jealous. Mine's been sitting in the shed since December. I want to work on it SOOO bad, but I have too many other things to do.

[81300R]

https://i.ibb.co/zGb3nK6/A897-D628-BDEC-4014-A2-B2-4-F92-B8720-BC3.jpg (https://ibb.co/bzL4Wpb)
https://i.ibb.co/DQxNsq6/AACD0-FE9-F277-494-D-BB93-7-A3286-F03-E89.jpg (https://ibb.co/GRKXBh1)

[ATC King]

Sounds like a rev limiter past 1/4 or so throttle.

It could be an electrical issue, especially at certain vibration frequencies, which I've dealt with myself. Those are some head scratchers. Loose connections can behave like that, fine at some RPMs but act up at others.

I'd be more inclined to look at fueling though. Two cycle engines will burble if too rich, it's something like a rudimentary rev limiter.

Small, two cycle power equipment is tuned from the factory to limit RPM by having the high side of the carb rich past a certain RPM. That keeps inexperienced operators from yelling at retail store employees because they didn't have a clue how to operate something because most everything nowadays is made to be idiot proof and that's what they're used to.

I've worked in a chainsaw factory and adjusted the carbs on thousands of saws.

If it's hitting a wall, check the carb over. When the company I worked for changed carb suppliers, we had a week of total hell. The first carb shipment was all over the place. Probably less than half of the new saws ran right off the assembly line. The repair techs at the end of testing were jumping through their arses replacing carbs and sending back through testing.

If that checks out, then attack the electrical gremlins.

[81300R]

It could be an electrical issue, especially at certain vibration frequencies, which I've dealt with myself. Those are some head scratchers. Loose connections can behave like that, fine at some RPMs but act up at others.

I'd be more inclined to look at fueling though. Two cycle engines will burble if too rich, it's something like a rudimentary rev limiter.

Small, two cycle power equipment is tuned from the factory to limit RPM by having the high side of the carb rich past a certain RPM. That keeps inexperienced operators from yelling at retail store employees because they didn't have a clue how to operate something because most everything nowadays is made to be idiot proof and that's what they're used to.

I've worked in a chainsaw factory and adjusted the carbs on thousands of saws.

If it's hitting a wall, check the carb over. When the company I worked for changed carb suppliers, we had a week of total hell. The first carb shipment was all over the place. Probably less than half of the new saws ran right off the assembly line. The repair techs at the end of testing were jumping through their arses replacing carbs and sending back through testing.

If that checks out, then attack the electrical gremlins.


When i first brought it home, i thought for sure the problem was the strange Blue Magnum carb it had on it. Played with that for a bit with no change. OK, ordered a PWK. Exactly the same issue. Doesnt quite sound right at idle and doesn’t rev up hardly at all/misses/holds back. Check coil grounds. Compression didn’t seem great so i pull the top end to find a polaris piston that comes up at least 1/4” shy of the cylinder deck. Bingo. Apparently that wasn’t it either :)

Definitely seems like an electrical issue. Going through stator and wiring before i order a cdi.

[atc300r]

Try another coil.I had an issue like this with my 85 250r back in 09.The trike would start and idle fine but over 1/4 throttle it would run like the choke was on.I tried different cdi,carbs,plugs,fuel that didn't work.I changed crank bearings and seals and new carb kit that wasn't it.When I tried a different coil it started running correctly. Just my 2 cents.

[81300R]

Try another coil.I had an issue like this with my 85 250r back in 09.The trike would start and idle fine but over 1/4 throttle it would run like the choke was on.I tried different cdi,carbs,plugs,fuel that didn't work.I changed crank bearings and seals and new carb kit that wasn't it.When I tried a different coil it started running correctly. Just my 2 cents.

I will do that. Thanks for the suggestion!

[ATC King]

When i first brought it home, i thought for sure the problem was the strange Blue Magnum carb it had on it. Played with that for a bit with no change. OK, ordered a PWK. Exactly the same issue. Doesnt quite sound right at idle and doesn’t rev up hardly at all/misses/holds back. Check coil grounds. Compression didn’t seem great so i pull the top end to find a polaris piston that comes up at least 1/4” shy of the cylinder deck. Bingo. Apparently that wasn’t it either :)

Definitely seems like an electrical issue. Going through stator and wiring before i order a cdi.


Good luck. Hopefully you'll find the issue without much hair loss.

I stopped testing any type of coils, be it a stator, pulse, ingnition, or anything that's wound with magnet wire, by the manual's resistance spec, years ago. A bit of bad insulation on the magnet wire may pass resistance specs, but with a load, they won't produce the voltage. That's why I test any of them by voltage anymore.

I've also not had the longevity out of any aftermarket stator compared to OEM. Rewinds of the stock stator seem to be more reliable. My experience is Chineseium doesn't last.

[81300R]

Stator tested good. Tried known good coil with same issue. Cdi is on the way.

Got it about buttoned up!

https://i.ibb.co/q7mRLrn/5-D08-C396-F867-49-CB-A516-A992-A894-A1-F0.jpg (https://ibb.co/17R9Ymn)

https://i.ibb.co/0fnzWF2/02-EB3-BD3-9-FB4-4-E48-B093-AD7406-BD5-DBE.jpg (https://ibb.co/64yqp1w)

https://i.ibb.co/34MFSx0/0721-A360-8450-4374-9051-E457233-E22-C1.jpg (https://ibb.co/n6n1QXD)

[shortline10]

Turned out great

[81300R]

Should of put these in the intro but this was when i crammed it in the back of my tahoe to take it home

https://i.ibb.co/608qFqh/5-B7795-B8-F9-F6-4-CCA-B1-C0-F99218-DF4812.jpg (https://ibb.co/3mvPcPX)
https://i.ibb.co/71tLk02/550-E174-E-C86-D-4783-B7-AA-1-B38-FE356522.jpg (https://ibb.co/5RhwKJB)

[81300R]

Good luck. Hopefully you'll find the issue without much hair loss.

I stopped testing any type of coils, be it a stator, pulse, ingnition, or anything that's wound with magnet wire, by the manual's resistance spec, years ago. A bit of bad insulation on the magnet wire may pass resistance specs, but with a load, they won't produce the voltage. That's why I test any of them by voltage anymore.

I've also not had the longevity out of any aftermarket stator compared to OEM. Rewinds of the stock stator seem to be more reliable. My experience is Chineseium doesn't last.



New used CDI did not cure it either.


Are there any specs available for what the stator should be putting out for voltage?

[81300R]

You guys will get a kick out of this…

I swapped stators with a spare. Same issue. Well its either in the harness or that damn supertrapp muffler.

Pull the muffler and it revs :p

So, even though i gutted the muffler, the disc baffles must be just restrictive enough. Funny because i have used one of these style mufflers on a 490 Yamaha in the past.

[81300R]

Modified a DG silencer.

Pretty much done except a kill switch and some jetting.

https://i.ibb.co/w7C9Yx5/1-C26363-C-056-A-4655-8-D0-B-D1-D36023-EA1-D.jpg (https://ibb.co/9h2FGCQ)
https://i.ibb.co/4FYVBQd/C2-D07-A37-4-BA4-4-DB3-8-C4-C-5-C4954-AC7-F54.jpg (https://ibb.co/qDWrbZ5)

[Footy]

Dang! Guess I jinxed you when I mentioned the supertrapp being for a 4 stroke.

[ATC King]

Dang! Guess I jinxed you when I mentioned the supertrapp being for a 4 stroke.



It wasn't the Supertrapp, it's that it was gutted. A muffler is a muffler, unless it's a large, empty shell, with an endcap, then the exhaust gasses dump into it from the mid pipe and velocity stalls, causing everything from there to pile up in the system. If it's just a core with no packing, there's increased turbulence, and performance suffers.


Supertrapps are sold for two and four cycle engines. I think the two cycle versions come with six discs and and twelve discs for the four cycle.



Regardless, trying to guess someone's issue on a trike that isn't stock anymore or has been monkeyed with is a left field guess. May as well suggest to check the fux capacitor.

[81300R]

Just for the record, the single shim fl350 headgasket made over 200psi compression. I put the full stack back in for pump gas.

Anyone running a similar setup that cares to share jetting their jetting?

Went from a 170 main to 155 and still breaking up rich on the top end. Assume i have other issues. Edit- definitely seems as if there is still an ignition issue on the top end. Digging into it again :)