YZ 400, 99. Engine noise/loss of power

Hey guys I've got a 99 YZ400, I need some advice please,

After noticing an oil leak during a ride and then a loss of power when accelerating I rode the bike home cautiously, the following day I was not home and my partner accidentally knocked the bike over and could not pick it up so it lay there on its side for about an hour. I also noticed the packing in the exhaust was damaged/loose.

I changed the oil and air filter and now the bike will not start. I roll started the bike but it stalled almost straight away.

Any ideas what could be wrong, any advice would be greatly appreciated thanks guys

Impossible to say

Not enough info

When was the last time you

- adjusted the valves

- serviced the carb and replaced the wear items

- changed the plug

I personally have never done any of those things to the bike, I brought the bike just after it had a full engine rebuild, and I've rode the bike 6-10 hrs since I brought it.

I suggest you get a factory service manual from Yamaha's website and start doing the basic maintenence.


That bike is reliable, but ALL off road bikes need regular service.


The words 'full engine rebuild' don't really mean anything without receipts and a description of exactly what was done, and by whom.

Thanks krannie that was my next move, I've just pulled the carby etc off and will be giving it all a good clean, I am normally extremely meticulous with maintaining my bikes, but having only just brought the bike and normally working interstate with only a couple of days off a month I haven't had the time... And I can't hold myself back from going for a quick squirt, so I suppose you could say I've learnt my lesson, thank you very much for your input KRANNIE.

Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now