spluttering

[marky19]

hi all, can any one give me some advice on my 1997 trx850
i have done a carb rebuild twice (full clean) balanced the carbs, done the air/mix, new inlet rubbers, all the valves are good and set, checked both coils and plugs, all vacuum and fuel pipes are good, new fuel pump and tap, throttle body is set,
it starts on the button straight away and idles fantastic but when i try to ride away it starts spluttering, can`t even get to second gear.
so on that note where have i gone wrong or missed.

[HolerTogni]

Hi marky19!

First, welcome to the forum!

Then, I guess (of course), the spluttering might have its reason in something fuel related, like (at least) one clogged main jet or a faulty fuel pump (although new).

Does she rev freely from idle in neutral?

Telediagnosing greets from Munich!

[marky19]

yes...........

[HolerTogni]

yes...........

... what?

I do prefer complete sentences.

I suppose you mean that she does rev freely from idle in neutral.

Also, if you pull up the throttle really fast?

"Trying again" - greets from Munich.

[marky19]

sorry i didn`t mean to sound rude, i wiil try and give it rev up tomorrow and let you know what happens.
thanks for your reply, any help is muck needed.........

[marky19]

hi mate, well i tried what you said and yes it rev`s up when i throttle slowly and when i give it a hard rev with no problems, but when i take it out on the road its starts to splutter cant even get to 4th gear and it fills like the engine is juddering.
and i have notice occasionally whilst idling i get a popping sound from the right hand side carb. (floats are set at 14mm)
many thanks again..........

[HolerTogni]

Hi marky19,

thanks for the detailed description of the behaviour.

My guess is still fuel and/or carburettor related, especially clogged main jet(s).
"Juddering" of the engine sounds to me like the balancing of the carburettors might need a further investigation (despite you said you already balanced them).

But if you are sure, everything is alright with the carburettors and fuel lines then I'm running out of ideas.

That said, this can only be guesswork from my side ...

While writing this, I do have a further idea:
Maybe there's fuel in the oil?
Not enough to completely lock the engine but enough to cause this behaviour?
Then a leaky fuel tap and most likely a leaky "float needle valve gasket" (don't know how it's really called in English) might be the cause.

Still guessing greets from Munich!

[marky19]

hi, thanks for your reply, you may have a point about the float needle gasket its worth a check or another kit and start again.
the reason im not giving up on this bike is because a friend of mine got me this very cheap a few years ago and now he has passed away, so with this bike i feel he is still we me. thanks for all your help again.....marky19....

[HolerTogni]

Hi marky19,

as Allen Millyard always sais: "You have to persevere and you will get there. in the end. "

Perfectly understanding greets from Munich!

PS:
Oh, please don't forget to check the oil for fuel in it! Seriously. It's easy, quick* and well worth it.
* A drop of oil on a cellulose "paper" (as you may use in your kitchen) and if you see a brighter circle around a darker one then you have fuel in your oil.

[dicky]

Some other things to consider...
Pretty much everything made of rubber will be starting to crack or perish, so check everything from the inlet manifold to the air box meticulously.
There is a plastic cap on the RHS carb that also cracks, the top of the air-cut valve. it can be bodged back together with epoxy if you can't find a replacement. I think Worlds End Moto had them.
The fuel tap/float bowl leak is a bugger to deal with. Simply replace the vacuum tap with a normal on/off/res tap and block the vacuum port on the inlet manifold.
Have the carbs been refurbished with a Factory Pro or Dynojet kit? If so, the jet needles may be the problem. These kits come from the US and are TDM kits, they never had TRX's and the profile on the needles is very different from the stock items. I've posted pics of this sometime in the distant past...
See also this thread https://www.trx850.com/phpBB_forum/view ... =5&t=12852