Difficult to cold start 350X

[Footy]

Trying to help a friend with his 1985 350X. It does not like to start when cold. It will start and idle for a few seconds and then die. You must repeat this process until it eventually warms up enough to run. Different pilot jets have been tried all yielding the same results. It is basically stock with a 400ex header and aftermarket exhaust. Any advice?

[Shep1970]

Tight valves would be my guess. Might be time to check them. low compression?

shep

[keister]

^^^^ I'm with Shep. When they don't start, it's the valves a remarkably high % of the time.

[Footy]

He says the valves have been adjusted and rechecked.

[Footy]

I ended up buying this 350X from my friend. It has an incredible lean pop on decell. We tried multiple pilot and main jets with not much change in the lean popping. I believe there is something going on with the float valve that is causing the float to stick, hang up or just move slower than it should. I have been able to start it cold after priming the carb.
The engine seems to run good otherwise and seems quiet (no ticking or slapping). It sure is a blast to ride through my tight woods trails.

[shortline10]

Are you sure their are no exhaust leaks ? That will also cause the deacceleration back firing .
As for the carburetor the easy solution it to just buy a new OEM 400ex carburetor .

[Footy]

Are you sure their are no exhaust leaks ? That will also cause the deacceleration back firing .
As for the carburetor the easy solution it to just buy a new OEM 400ex carburetor .

I will check for an exhaust leak. I have thought about using a 400ex carb. is there an intake boot that makes this easy or do you have to stretch or modify the stock 350x boots?

[MrConcdid]

Hey Footy,
I will second the 400ex OE carb. Like others have said valves contribute to a lot of carb problems.
I will tell you I had a crack in my intake boot, between the carb and head, they tend to dry out and split.
Also if you put the 400ex carb on. I recommend using grease on the inside of the intake and a heat gun
the 400ex carb is bigger than OE.
Great upgrade!

[Footy]

Hey Footy,
I will second the 400ex OE carb. Like others have said valves contribute to a lot of carb problems.
I will tell you I had a crack in my intake boot, between the carb and head, they tend to dry out and split.
Also if you put the 400ex carb on. I recommend using grease on the inside of the intake and a heat gun
the 400ex carb is bigger than OE.
Great upgrade!

Thanks for the tip. Can you still buy the intake boot new?

[MrConcdid]

I bought a good used one. you can find them on ebay and also check out the FB group "King of the Hill" ran by Lou Bothello, he has a ton of 350x parts.
I believe the intake for the 300d is the same.

[Footy]

I bought a good used one. you can find them on ebay and also check out the FB group "King of the Hill" ran by Lou Bothello, he has a ton of 350x parts.
I believe the intake for the 300d is the same.
I am going to assume you are referring to the TRX350D 1986 or 87?

[MrConcdid]

I am going to assume you are referring to the TRX350D 1986 or 87?

Oops yes 350D.