Jump to content
Sign in to follow this  

Power loss at full throttle pinned 3rd gear? jetting or other prob?

Recommended Posts

Hi, i was out riding tonight and towards the end of the night (after an hour riding). when i was hitting the 90ft step up in 3rd gear pinned (the lead up was rutted so the bike got revved out sort of fast)

the whole night i was hitting it no probs and the bike sounded fine and would rev out okay.

then at the end it sounded like it had no fuel, as if the fuel line was clogged so i pulled off and revved up my bike and then it wouldnt take full throttle and would not hit the rev limiter but make a weird sound.

at 3/4 throttle it would hit the rev limiter..

im not sure if i need to re-jet a little, im not sure where to even make minor adjustments even, do i lean or richen?

or maybe it was a dirty air filter? i only put an hour ride time on but it was a failry dusty day?

i have been told before that on a straight when i chop the throttle it does backfire a little - are these 2 things related?

advice? thanks

also: i have never had a probelm with bogging even after riding in the sand for an entire day??

Share this post


Link to post
Share on other sites

Well-tuned bikes tend to pop on decel without an ACV.

It sounds to me like it's leaning out past 3/4 throttle.

Some things come to mind:

air cleaner (check that it's clean)

Spark plug: clean or replace

Carb: clean jets and emulsion tube.

Give it a bash after each of those and see if that takes care of it.

Share this post


Link to post
Share on other sites

so from what you are saying is that its probably not a jetting problem here.

which would make sense since the bike was running fine ALL day long and on the weekend too with no problems.

the air filter was dirty, so maybe that was a big chunk of the problem?

maybe it was some dirt running through the carb?

but you are recommending not to make any carb adjustments?

----what are those quick adjusters that you can buy that go under the carb called? are they worth anything?

thanks again

Share this post


Link to post
Share on other sites

Well, I'm kind-of saying that. I dont' think that you need to change your jet settings, if that's what you mean. :thumbsup:

Here are my reasonings:

If the air cleaner is clogged, the bike will run rich and might not be able to pull enough air at WOT to rev up. Cleaning or replacing it eliminates it as a source of the problem.

If the spark plug isn't reasonably clean, the bike can have issues with a lean or rich mixture that it could otherwise handle. Replacing it eliminates it as a source of the problem (you can see where this is going...) :busted:

If it isn't either of the above, it sounds like your main jet (circuit) is partially clogged and limiting fuel past 3/4 throttle. This will tend to make the bike run lean past 1/4 throttle and get worse the wider the throttle is opened. Taking the needle and main jet out and flushing the emulsion tube and those parts should help with that.

Dirt can also get into the air jets (inside the carb intake bell) and make the bike run funky.

Another thing to check is the float valve to see if the valve or screen is clogged. If the bowl fuel level can't keep up with demand from the main jet, the bike will also run lean and can suck air through the MJ at high throttle positions. Some dirt in the gas tank might have gotten into the carb. Back-flushing air or carb cleaner through the float valve should push any junk in there out.

The fuel screw is the quick adjuster that you're mentioning. Yep, they're definitely worth the $20 and really make it easy to adjust the pilot circuit as temperatures change during the day. The TT store sells several versions of them.

Good luck with this. It's probably something really simple - just a matter of grinding away at things until you find it. :thumbsup:

Share this post


Link to post
Share on other sites

Thanks for the advice David9999 thats much appreciated. i will try to work though some of the issues tomorrow taking the carb apart and giving it a good ole' clean.

it has 20 hours on the bike so maybe its time?

one thing i should mention that i dont usually use is: i was using a twin air filter (like always) and i put on a filter skin - the skin seems like it is made of a more dense material than the filter making it easier to clog? perhaps that was the problem and why it may have been starving of air?

just another thought?

Share this post


Link to post
Share on other sites

Filter skin: It's not supposed to do that, but there is less surface area on them so maybe that's it.

I don't use a filter skin unless I'm riding in sand. I usually just wrap my airbox in a pantyhose leg for that anyway. :thumbsup:

No brakleen in the carb btw. It tears up the seals. (forgive me if you already know this)

Share this post


Link to post
Share on other sites

I agree with the Air filter since the bike ran fine earlier..

When i had 04 125SX i was hitting a step on step off triple. and the triple was pretty close to a wide open jump

at the end of the night i was soing it one more time and i landed the stepoff, pinned it, backed off real quick, and pinned it...

The bike bogged and then would not rev out clean......i didn't make the jump good

Cleaned the filter and the next time i was at the track no Problems

So clean your filter and check it,, i bet it will run fine after that

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  

×