Jump to content
Sign in to follow this  

KTM 85SX difficult to start

Recommended Posts

Our 2006 85SX has become very difficult to start.

Compression is good at 154 psi with throttle open and bike NOT warmed up.

Carb has been cleaned and reeds checked for damage.

New plug doesn't help things.

Plug turns a glazed chocolate brown on center electrode porcelin after a short time (should be fuzzy, not glazed).

Once started, bike starts first kick. Left to sit overnight, it's a miserable effort getting it going with many down-the-hill-let-out-the-clutch efforts.

Bike also seems to smoke more than it should (whitish gray smoke).

I am suspecting crank seals. Possibly the stator side leaking air and making the mixture to lean to start when cold, and/or possibly the clutch side as the tranny oil could be causing the smoking.

I noticed the tranny fluid seemed to have some water in it, so that tells me the water-pump seal needs replacing. If that's the case, then it makes sense to me that the crank seals also might be going as they are all the same age.

So I am about to order seals (and clutch cover gasket, etc.), but before I do, has anyone any other ideas on what makes this engine hard to start?


Share this post

Link to post
Share on other sites

sounds like you have a good handle on it.

the only other thing I can think of is float level too high, but I suspect you would see other symtoms of that if it was the case.

Share this post

Link to post
Share on other sites

Thanks for the vote of confidence. Parts are ordered and should be here next week.

I checked the float and it was fine for a dry check. I suppose it could sink (can't remember now what it was made of), but probably not float higher.

I was thinking of changing one seal at a time, but I probably won't. It would be interesting to see if different seals cause the different symptoms or not. i.e. clutch-side crank seal causes the smoke, stator side causes the hard starting.

It wasn't long after this problem came up that I had to do a top-end on this engine. Ground elctrode on the plug broke off due to detonation and banging around in there pinched the piston on the ring and lost compression. From what I could tell, the combination of a higher CR Wiseco piston plus the thinnest cyl base gasket were used by the previous owner. I used all KTM parts when I did it.

So now I wonder if maybe the detonation was caused by tranny oil getting in there. The mixture seems good, so I don't think it was a "too lean" issue.

Guess I'll never kknow that one, but changing all these seals will hopefully get everything working properly.

ps: Crank seal wear is often an indicator or crank bearings going bad, but I checked that during the top-end work and it seems tight...no perceptible movement at either end of the crank and the dial indicator showed tight rod clearances too.

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