Jump to content
Sign in to follow this  

My bike won't cold start

Recommended Posts

Went riding this weekend to juniper dunes, First day my bike ran great but the second day it wouldn't cold start. I know it about time for me to do some work on the piston and rings cause its starting to eat up oil a lot faster. But the second day, the bike had hardly any compression and wouldn't cold start. Luckily I could just roll it down a hill to start it up. Once it was hot though there was know problem kicking it over and running, I did half to turn the idle up a little bit to keep it from dying when I wasn't on the gas. But that was all temporary for the day until I get things strait. Any one have any suggestions of what might be going on before I tear the top end apart? Cause I've never had to do this before.

Edited by tanner49crf250

Share this post


Link to post
Share on other sites

Intake valves are shot. Replace them unless you want to have them re-shimmed and they may last another 2 hrs if your lucky.

Share this post


Link to post
Share on other sites

OK, now here's another question. Should I invest in titanium valves or stainless steel? Which are better? And since my top end will be apart should I replace the piston?

Share this post


Link to post
Share on other sites
OK, now here's another question. Should I invest in titanium valves or stainless steel? Which are better? And since my top end will be apart should I replace the piston?

If you ride hi-level MX, titanium valves are what you want to use. C/slower B rider, stainless are good. Regardless, the valve seats will need to be cut. New piston and rings along with a new timing chain is always a good idea. Specially if the engine has over 50-70 hrs on it.

Share this post


Link to post
Share on other sites

Ok, I have far more than 70 hours on it. I knew this stuff was going to happen and I was counting down the days cause its about due for all this but it just happened at the worst time possible. I'm planning on taking the head apart this weekend. what are indications that the piston and intake valves are shot?

Share this post


Link to post
Share on other sites

With what you described, your bike is trying to tell you something. If you have to bump start it and u have low compression, you are gonna do more damage to the engine. Like the guy before me said, go with steel valves, not much weight difference that will effect you and they will last longer.

Share this post


Link to post
Share on other sites

Yeah I knew that. I only rode on it for a couple hours but I couldn't just go home on sunday. Im not riding it till I figure everything out, its time for pretty much a new top end anyways.... it needs one and prior to memorial day weekend I was planning on throwing in a top end anyways.

Share this post


Link to post
Share on other sites
If you ride hi-level MX, titanium valves are what you want to use. C/slower B rider, stainless are good. Regardless, the valve seats will need to be cut. New piston and rings along with a new timing chain is always a good idea. Specially if the engine has over 50-70 hrs on it.
Not trying to hijack-is the OEM timing chain adequate, or is there an aftermarket one that is better? Doing a top end and head rebuild next week.

Share this post


Link to post
Share on other sites

Hope this isn't too late, my computer has been down. The OEM timing chain is very good. As good as any other you can buy.

Share this post


Link to post
Share on other sites

You don't necessarily need to replace your entire top end. It just sounds like you need to shim your valves. I really have no idea why Charles is telling you to Replace everything if you haven't even checked your valve clearances. Check your valve clearances I bet that is your problem. No need to replace valves and piston if you don't even know If you need them. Take off your cam cover and check the clearances it takes literally 10 minutes.

Share this post


Link to post
Share on other sites

Do your valve clearances and re-shim where necessary. Don't be surprised if this is a short term fix. If they do tighten up after a few hours, then new valves are the order of the day. See how it goes.

Share this post


Link to post
Share on other sites

By the time you need to shim the valves on these machines, the seats are shot(or soon to be)

Share this post


Link to post
Share on other sites

Yeah. I agree with you there. I believe its just the valves, so I'll be replacing those once I get my paycheck. But the 250 is a 04 and it eats up oil quite a bit now. So its probably just a good Idea to get a new piston and seals. But not an entire new top end. Any recommendations on pistons? O know im getting forged and Im not going OEM. But other than that im kinda drifting.

Share this post


Link to post
Share on other sites

Is it even worth re-shimming your valves or should I just get new ones?? I was looking at kibblewhite black diamond valves.

Share this post


Link to post
Share on other sites
Yeah. I agree with you there. I believe its just the valves, so I'll be replacing those once I get my paycheck. But the 250 is a 04 and it eats up oil quite a bit now. So its probably just a good Idea to get a new piston and seals. But not an entire new top end. Any recommendations on pistons? O know im getting forged and Im not going OEM. But other than that im kinda drifting.
I am not an expert, but if you read posts on this sight most people will tell that simply installing new valves is a short term fix. If the seats are hammered, you have to to have new ones re-cut. I know it is somewhat expensive(I have been looking at this myself), but personnally I would just bite the bullet and have the head rebuilt by a competent shop. Of course, you wont know until you have it apart. As far as the piston, JE, Wiseco seem to be recommended-and pretty much all of the aftermarket ones are better than stock. Just tore into mine this weekend, and the stock piston is nothing more than a cast one(I beleive)

Share this post


Link to post
Share on other sites

OK did some work today on the bike. And I have no valve clearance on the intake or the exhaust valves. Now that I know this is the problem should I just re-shim them or get new valves and have the seats cut? What would be the best choice?

Share this post


Link to post
Share on other sites
If you ride hi-level MX, titanium valves are what you want to use. C/slower B rider, stainless are good. Regardless, the valve seats will need to be cut. New piston and rings along with a new timing chain is always a good idea. Specially if the engine has over 50-70 hrs on it.

As I stated before. If you go any other direction like re-shimming the valves, you'll be doing it again very soon and after doing it the third time, it should last you maybe 1 ride and they'll zero out again. Re-shimming the stock titanium intake valves just bandaid's the problem for a short amount of time. Some get 5 hrs and some get 30 minutes out of a re-shim.

Don't listen to anyone that tells you the intake valves are fine, they're done and replacing them and having the seats cut is the only fix.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×