A forum for owners of Yamaha TTR250 trail and enduro bikes!

tom438596 · Member

hard start

Pendo · Veteran Member

Hi Tom

I'm no mechanic but I have read on a few forums it could be worth checking that the valves are in spec.

Does the bike idle fast when warmed up? I had an old Honda XR that if the idle when warm was fast, it was hard to start when cold (would flood easy). Could never give it any throttle when trying to start cold. Formed a bit of a habit, so I never use any throttle on cold start with my TTR, just full choke.

TTRfan · Super Guru

Is the choke mechanism working? A simple test is to pull out the choke when the engine is hot and see whether it makes the TTR run rough.

Brian

AGman · Veteran Member

TTRfan wrote:
Is the choke mechanism working? A simple test is to pull out the choke when the engine is hot and see whether it makes the TTR run rough.
Brian

This is what I'd be doing first...

tom438596 · Member

Hey Brian. Glad to see your the first to reply after seeing all your great answers on other people's problems. The choke is working. Though it does sit out abut and have maybe 5mm of the rod showing, Is this normal?. I have cleaned carby, changed spark plug, and air filter. Also changed the inlet manifold stub......is it possible that my mixture is so far out because someone has changed it due to the extra air from the busted inlet manifold??? The valves are definatly my next bet pendo. I'm just scared to touch them.

TTRfan · Super Guru

A few more simple checks:

Does the engine stumble or react differently if you pull the choke fully out whilst riding it? If not, it is likely to be the problem.

If you lean the bike over until petrol comes out the overflow, does it then start OK? If so, it again points to a choke problem.

What sort of mileage has the engine done? If high, then it could be low compression that is causing the starting problem . If you haven't got access to a compression tester then a simple check is to remove the plug and turn the engine over with your thumb over the plug hole. The compression should be good enough to really force your thumb off the hole.

It is straightforward enough to check the valve clearances. Lots of good info on valve clearances here. You will need a good feeler gauge such as here. If you find they are out of spec then you could get a local bike shop to make the adjustments if you don't feel confident enough to do it yourself.

Brian

tom438596 · Member

Ok so I put the air filter in today freshly oiled thinking that having it off was impacting the starting. I can't even get it to start. It ran great before other then being hard to start when cold and revving higher gradually. Please help!!!! Should I clean the car by again??

tom438596 · Member

Thanks Brian I'm going to try to check the valves tonight and I will do the compression test now.

tom438596 · Member

Compression is OK :)

tom438596 · Member

I can't do a valve check that's out of my caper Lol. I'm a builder and the carby was fairly challenging. I didn't clean the main jet in the car by though.....would that be the problem?

TTRfan · Super Guru

It is not unusual for a freshly oiled filter to prevent starting. I try to give them a little while to "dry off" a bit before installing. Helps to have two filters - one in the bike and another clean and oiled on standby - kept in a plastic bag to keep clean.

It is unlikely that a problem with the main jet would cause starting problems. OOI, does the TTR run OK once started and warmed up?

Good to hear the compression is OK - that rules out one possibility!