Working on a bike... CR250

[DougTx]

Hey guys,

Really looking for some advice here. I have a strong XR400 I ride and love for trail. Nothing much to do to it and I wanted to learn so I got a 1988 CR250. It is a little rough but it runs, it smokes on start up, won't idle, smokes but less when it runs and I have seen a little bit of wet black soot/oil on the read fender behind exhaust (it starts on second kick and I can ride it but man it is like chitty-chitty bang bang).

I bought it to work on and learn and paid nearly nothing for it.

I ordered a Clymer manual and am willing to spend some money and time learning. Any good ideas on books, websites etc on learning to rebuild and fix up a bike?

I have tools and basic mechanichal knowledge (built a few street cars in to race cars etc).

I think it will need a top end at least? Carb re-build for sure but hey, that is what I want...

Any advice or thoughts other than give up now are appreciated... :)

Many thanks everyone....

Doug in Dallas
2002 XR400R (love that thumper)
1988 CR250 ...well.. it could be good one day for a learning tool

 

[Chili]

Won't idle or is not set up to idle? Most two strokes owned by racers are set to not idle and will die after 5-10 seconds with no throttle.

The smoking and black spooge is likely rich jetting. I'd start with a compression test and a thorough carb cleaning. Then do the top end whether it needs it or not since that was the reason for the purchase.

Then I'd start looking at all the bearings to make sure the bike is safe to ride. Good luck and have fun :cool:

 

[_JOE_]

http://www.ericgorr.com/

There's clickable links with tons of info.

What do you plan on doing with this bike? Are you looking to get really deep into trying to fix it up or just get it running reliably?

Look closely for cracks in the frame, swingarm, etc.

 

[DougTx]

What do i plan to do with it

Good question,

Since I know how to ride but not much about building/rebuilding I was hoping to get it running correctly and have some fun riding it while also learning about jetting carbs, doing engine work, suspension, forks etc.... I will get as deep as I need to but I have no plans for the bike being anything more than a trail riding, fun to mess with, guest bike when freinds come to ride kinda thing.

Thanks for the advice on craks etc... I will look, any common places of concern I should check?

My initial plan was.
1. Check compression
2. Find out what is the facorty carb so I can order a rebuild kit for it if one exists (I believe it is a Keihin PWK38mm but not sure) to learn to rebuild a carb....
3. Check the reeds etc, clean the pipe and get all of the crap out of the exhaust (it sprays some nasty junk so it probably is not pretty)
4. If it needs one do a top end.... that seems to be pretty commonplace for two strokes....

See if I can make it run right. Once that is done...

Then invest in, front,read and swingarm bearnings, recharge of suspension, check the fork seals, put some tires on it....go for some rides and learn more about making it run right.

I am really a novice here so if you would like to interject some steps I am missing, I dont want to buy or do anything if the engine is shot, case is cracked, something that will make this a no go down the road... if it takes me a year to finish that is ok to.. it is as much about me learning to work on my own bikes and about what is a good and bad bike to buy as it is for me to have a motorcycle. I have no illusions about racing it or selling it for a profit or even break even. It was just for the near nothing I have in the bike it seemed a good bike to try to learn to build and fix on and have some fun in the process.

Hope that makes sense....and thanks for the advice.... I am surely going to need it... I ahve the XR400 for riding when the building/becoming pops racer gets to much to handle... :)

:cool:

 

[00KX250Byrd]

Be careful! Once you get that 2T 250 running good, you may find yourself riding it more than your XR400.
Britton

 

[DougTx]

Hey that wouldn't be so bad.....

I am open to 2 stroke vs. 4, I just love my XR because I ahve always owned and ridden XR's in my life (well only 3 bikes total an XR100,XR200 and this XR400)

Two bikes is a happy thing I think.... :laugh:

 

[_JOE_]

I was hoping to hear just that! :cool:


Try not to rush anything. Before you turn wrench on the motor have someone do (or buy yourself) a leak-down test. It will tell you if the crank seals are sealing. This is critical to the bike running correctly.

Buy a new top end kit. Tearing it down without replacing the hundred dollar piston is silly, not to mention a dangerous gamble. When you get it apart have the cylinder measured by someone with proper tooling and closely inspect the cylinder for scoring or other damage. The last thing you want is to put a new piston in a worn bore and end up with skirt breaking off and junking the crank and cases.

Make sure you check the tolerances on the crank while the top end is off.

It sounds like you want to do this right, so if it seems like something doesn't look right make sure it is right before you run it.

A digital camera is great so if you have a problem or think something looks wrong you can post up a pic and get some input.

 

[jdager]

top end is probably gonna be a must on a bike that old, and if nothing else, take it apart, closely inspect and measure the piston and cylinder, and replace the rings. get a dealer service manual, if you look around, sometimes you can find one to download for free off the internet, but I have found a service manual much, much more helpful than a clymers. I would take the carb all apart, clean it out good with carb cleaner and compressed air, and you may or may not need a rebuild kit (I dont know how common these need to be done). for the exhaust, I would take the silencer apart and repack it, since it sounds like it is filled with black splooge (a little can be normal, but excessive amounts indicate the bike is running rich). once you repack it, I would not ride it much until you get the carb cleaned/rebuilt/jetted correctly, or you will just refill your new packing with new black splooge. once you get the engine worked on and put back together, make sure you properly jet your bike, look for sparkeys jetting guide, and get your bike jetted according to that, it will make a big improvement. thats all I can think of for now, someone correct me if I said something that is incorrect, I am still learning myself,
Jim

 

[DougTx]

Honda Service Manual

Well I got the Clymer manual today and was hoping to use that since the only factory CR manual I have seen so far was from Honda and kinda expensive.

If anyone has one to sell/loan/know where to get one at a reasonable price, or PMpost where to find an online one that would really be great.

Sunny and 70's today...can you say ride then come home, have lunch and start working on the CR?

Thanks guys, I gotta tell ya' I am pretty excited about this. I am tying to not be overly optimistic but I have tools, the internet, a Clymer manual and patience...

Thanks for the advice on shooting digital pics and posting them for advice... I may do just that....

Hey I saw online that the packing for the exhaust is wool/material according to the Honda parts fiche... Is that a common thing I can buy or do I need to buy specifically for the bike or for that bike?

Talk to you soon....

 

[KTM Mike]

Sounds like you have already gotten lots of good on the mark advice. The Clymer manual will do - maybe a factory manual might be a tad better, but at least you have something.

Setting aside any internal issues (ie low compression, bad crank seals etc. - both of which should be checked as others suggested), to me it sounds like all it needs to run well is likely a good carb cleaning (my guess is it is gummed up from sitting), and maybe toss in a new spark plug. If the carb is gummed up, or if the jetting is set up way wrong, it would easily cause what we call "spooge" - the black oily gunk coming out of the exhaust. 2 strokes do that when there is a jetting issue. Cleaning a carb really is not that hard. Remove the carb from engine, remove float bowl - look at the bottom of the carb with bowl removed. You are now seeing the main jet in the middle stick up towards you then kinda beside it, is the pilot jet. You might get lucky and not even have to remove the jets - buy some carb cleaner - spray out every orifice you can find. I would still remove the jets though - the main will come out with a 6mm socket (I think that is what it is) the pilot simply takes a straight tip screw driver. Put it all back together - viola - good running bike (hopefully).

Also be sure to check the tranny oil - change it! Look to see if it appears millky/grey or frothy - this would be bad news - means coolant has leaked into it via the water pump, or some other seal going bad.

The exhaust packing it typical - more like a fiberglass material. Dont just use regular fiber glass though! FMF, Moose and many other aftermarket parts makers sell silencer repacking materials. Stop by your local shop and tell them you need to repack the silencer on a 88 CR250. The actual material is somewhat generic - the difference is the length of it, and maybe how much material is packed in it. Dont worry about buying OEM repack stuff. Aftermarket is fine. Consider bringing your silencer with you so you can size things up - there is a good chance it has some sort of aftermarket silencer on it. Dont cheap out on repacking the silencer - you want that bike as quiet as you can get it! It is quite easy to do - do some online searches for repacking silencer (here on DRN is a good place to start), or look in your service manual.


If you plan to trail ride the bike - find out what the legal requirements are in your state. Here in Michigan, there is a set noise limit (94Db), and you must have a spark arrestor (good chance your CR does not have one), and you must purchase and display on the bike a state issued ORV sticker. You can buy a Cobra Sparky add on spark arrestor if needed, or you could replace the entire silencer with one that already has a spark arrestor built in.

Once that CR is running properly, you will be absolutely amazed at the power difference vs your various XRs - totally different animal - like double the power output. 2 strokes such as the CR vs a relatively "old school" XR 4 stroke are way more powerful and the power delivery is much quicker.

 

[KTM Mike]

oh, by the way - the smoke on start up is typical with a 2 stroke - once they warm up, the smoke should die down somewhat but likely does not go away entirely. That is the oil mixed in the gas burning. Be sure you mix oil in the gas. 40 to 1 ratio is what I use in all my bikes -buy a good name brand of 2 stroke oil at your local dealer.