Non Cold Start 1991 KDX250

[kdxer250]

My 1991 KDX 250 only starts when cold when I drop a bit of premix into the plug hole, then it starts 1st or 2nd kick, and starts ok for the rest of the day. Im thinking crankshaft oil seals but as some muppet at Kawasaki fitted the seals from the inside of the crankcase and because Im far from 100% on my diagnosis Im seaking advise. Also do any of the KX gasket sets fit?. ;)

 

[julien_d]

I think you can use some kx gaskets of the same years. Some people use kx head and/or base gasket and it raises the compression a touch.

It could be crank seals. Are there any other signs of leaking crank seals though?
Excessive smoke?
Using transmission oil?
Premix residue behind the stator cover?

If none of these things are evident, I'd look at fuel delivery. Since you said a shot of fuel in the cylinder fires it up, I'd expect it's not getting enough fuel. Pull the carb and clean every passage. Blow compressed air through them backwards to clear them out. Guitar strings work well as carb cleaning tools too, just be careful not to scratch or mar any surfaces. Pay special attention to the choke, since it is critical to cold starting.

Of course, make sure compression is good and airflow is not restricted either. Reeds that don't seal can cause hard starting issues too.

Sorry, this is all pretty basic stuff. Pretty easy for you to check though if you haven't already. Oh, and congrats on the 1st post. good to meet ya :cool:

 

[dirt bike dave]

If the bike used to cold start fine and has progressively gotten worse, it is my experience that the most likely culprits are bad reeds, or low compression due to worn out rings. Both of which are mentioned by julien_d.

Any cracking or warping of the reeds can make a bike an absolute bear to cold start. It will usually warm start fine, though.

Your bike can use a head gasket from an '88 KX250, which will give you more compression and low end power. Other years may work as well (89, 90, not sure about '91) but the '88 is what your motor is based on and it had a 'thin' gasket standard that year. Some years of the KX have an optional thin gasket, with a standard head gasket that is not much (if any) thinner than what you have. So if the dealer gives you a choice on thick or thin, get the thin one.

 

[julien_d]

Thanks Dave. I couldn't quite remember how that went with the head gasket, but I knew there was something there.

 

[dirt bike dave]

I kind of miss my '91. It was an overly rich, poor turning, badly suspended overweight bike with a bad riding position when I got it.

After getting it dialed in (lot more work than most bikes), I really liked the bike. It was very reliable, had good low end power and tremendous range for a two stroke with a stock tank. It made a very good dual sport bike. FWIW, both my '91 and my buddy's '92 had stock fuel tanks that measured at 3.6 gallons.

The extra grunt compared to my '90 200 was much appreciated hauling my butt over some high altitude, steep trails.

Never really fixed the overweight part, though. With all the guards, heavy tubes and dual sport kit, it was about 255 lbs no gas, and that was with an FMF pipe and Answer silencer. Add 5 lbs with the stock pipe/silencer. Could get it down to maybe 250 lbs in trail trim.

 

[kdxer250]

Thanks for the advise I will take a look at the weekend wife permitting (Ive got decorating to do !).

 

[Tom68]

Mines been a bear to start cold (do a search on SR models and you'll see it mentioned) Put an NGK 9 iridium in it for a ride 3 weeks ago, read your post now and thought I'll go give it a kick, (1st in 3 weeks) 2nd kick she fired, use to take 15 kicks, petrol had been left on as well, may have helped.

 

[kdxer250]

Yes an Iradium plug did help me for a while but has now gone back to non starting

 

[kdxer250]

:nod: Hi I have now changed the crankshaft oil seals, main bearings and reeds, correctly alligned the power valves and put it all back together and guess what ? yes it still wouldn't start properly but does go a lot better. In a fit of desperation I bought a new choke plunger and yes all is now OK. I hope this may help somebody else suffering the same symptoms. Result 1 x happy KDX 250 + 1 x happy owner.

 

[EncyclopediaRonnie]

:nod: Hi I have now changed the crankshaft oil seals, main bearings and reeds, correctly alligned the power valves and put it all back together and guess what ? yes it still wouldn't start properly but does go a lot better. In a fit of desperation I bought a new choke plunger and yes all is now OK. I hope this may help somebody else suffering the same symptoms. Result 1 x happy KDX 250 + 1 x happy owner.

now 1 most likley angry wife cause you keep going riding ahahahahah :cool:

 

[kdxer250]

:nener: Nah Just glad to see the back of me probably. :ride: