Lifan auto-revving option... :?

[AKTV8]

Been playing with my Lifan 150 Enduro and I like it except for this autorevving option that came with the bike. Don't remember ordering that but they threw it into the deal anyway.

The engine rpm just takes off most of the time from my idle setting of 1800 to around 4-5000 rpm and stays there. Found that by leaving it in gear and rear braking, it will "force" the rpm back down to idle. I am running it like this and braking to idle the engine but not really the way to go.
Throttle cable doesn't appear to be sticking and I made sure that the slider fit into the carb bore properly, so....

Anyone have a similar experience and what is the fix?
I like this cruise control while trail riding but have a feeling that is is hurting my $100/barrel crude fuel economy! hehehe
Hmmm, taking the carb out isn't appealling to me right now, but I guess that I should not complain as I have AZ weather to do it in...

Happy New Years all!!!
_________________

[TeamCheap]

Maybe a leak(air leak) between the carb and cylinder.

If all else (throttle/cable/slide) is working smoothly like you said it could be sucking air in somewhere that it shouldnt be.

[Gasoline]

Yeah, it sounds like a leak. Takes air so check your ???? the rubberthings that keeps it tight (man I gotta learn those words in english) between the cylinder and carb. Check the fuel/air mixture screw, may have fallen out totally. And also check the lock for the throttle, so it's tight.

[AKTV8]

Thanks, but I how do I find and stop this ghost?
I know the starter fluid gas trick around the suspected phantom.
Are there gaskets or sealant to use??
And of course, why does this make my rpm go up? Wouldn't it be like my choke and more air would cause it to bog and rpm go lower?

I was suspecting my float valve in the bowl but the, why would using my rear brake (front doesn't affect) while in gear bring it down?

[IronFist]

Is it a .....Manafold Manifold?

I heard you can use wd40. It seals the leak and things run well for about a minute. It's only to help you find the leak so you can tighten or replace the ...Leaky bits. JMHO. I don't know much, just saying what I'd try. N2r.

[Gasoline]

I suspect that your rpm rushes because it gets more air and less fuel. What happens if you use the choke?

Otherwise, if you want to make sure it's sealed.. there are ways but I suggest detach the carb, and middletube if any, check all gaskets or those rubber-rings, check the lock on the throttle so everything's tight.

But then.. if it still runs up in rpm while using choke.. then it beats me. If it's one of those chokes that these bikes seems to use, the one that almost closes the carbs airintake.

[TeamCheap]

Nope it sounds like an air leak to me and when it sucks in more air from somewhere it shouldnt it will run lean which will make it screaming fast but it can be very damaging to an engine.

Find the air leak, check carb and intake manifold.
Anyway it sounds like it is getting air in from somewhere it shouldnt.

You could just check the intake manifold bolts and if they are loose tighten and see if it helps or just take the carb and intake off and give it a good looking over.

If you do the spray trick and it doesnt change anything do a visual on the carb and intake yes that means taking it off in the AZ weather you have and be thankful you dont have the 10.5 inchs of melting snow/mush I have.

[IronFist]

Like I said it won't change anything, it's only used if you are having trouble locating the leak after a good visual inspection. :oops: sorry sorry sorry.

[TeamCheap]

new2riding the spray trick is a valid test but even if it doesnt show any change he should check the intake.

So if it were me I'd just go right to the removing of the carb and intake tube and give it all a very close inspection.

I learned a lesson from my gas cap vent being plugged which was: a complete and thorough inspection of even the smallest things can lead to the problem and then solution.

[AKTV8]

Thx all for the response. (Hey Capt. Canuck, I'm originally from MTL, but don't tell anyone, eh?)

The phantom air leak just doesn't seem plausible - I don't believe in what I can't see! I prefer tightening bolts to removal and inspection, getting lazy in my old age. So if the case, why does rear braking in gear bring the rpm back down to normal? Sorry, I have this logic comprehension syndome thing happening. Gotta know why...

So disassemble, inspect, retighten I must. The WD40 thing is like the engine starter fluid, good idea.
I suppose I should be thankful it is just that.
Sticky, sticky, leaky, leaky... more torque, we need more torque!!!
The solution to every problem!
Anything else will overtax my cavemen brain....

[TeamCheap]

Well I did have one other idea for the unwanted rpm's and since you said in your first post you have already checked the cable, throttle and slide all I had left was the air leak and ....well......but it's so out there, so hair brained, so so so STUPID I didnt bother but it's good for a laugh.
So here goes. :oops:

I briefly thought that maybe your bikes CDI had gone loopy and was somehow causing an ignition advance causing the RPM increase.Maybe the rear brake light circuit was causing it to idle back down drawing power from the CDI. (umm yeah I DONT THINK SO )



Ok but really if the bike is in gear and you apply the brakes it will slow the bike down and eventually stall it.If the bike is revving and you slow it down by braking and then pull the clutch in it should rev back up if something is causing it to throttle up.

[AKTV8]

So I give her gas, and up goes the rpm, even when I back off the throttle.
She still maintains 4000rpm. And if I apply the back brake while in gear, she will within a few seconds idle back down to 1800 rpm which she will maintain until I hit the gas and then away she goes again to 4000rpm until I repeat the breaking procedure.

Notice how I use "she" to relate to a difficult, stubborn problem??? Must be some kinf od Fruedian slip.

If it was an air leak, would it not be constant and always run up?
So when I stop, I brake the rpm back down to idle and in neutral, she maintains idle until I hit the gasoline.

I will check for air leaks tomorrow as they are giving better weather.
Thx for the help. Has all that snow melted in Michigan???

[TeamCheap]

OK answer this:
With the bike OFF and you just walk up and twist the throttle to full throttle then simply let go, does it snap back right away??? all the way???

You said you made sure the slide fit the carb bore right and there was NO binding from the throttle but did you happen to notice if the clip/washer/retainer that holds the needle in place in the slide was under the carb slider spring.
Just a long shot but if that clip isnt holding the needle in place in the slide I suppose it could idle up on you.It would be running rich then I'd guess.

I'm guesssing a look at the spark plug would tell if it is a lean running condition or a rich one.

Yep, snow is gone except the snow piles but it looks as if it will be back this weekend and if I get off my rear end and get my quad put back together we could take our quads out for a ride in it.

[AKTV8]

thx for the input teamcheap. Like that name btw, gutsy.
So, today's work in lovely 65 weather (gottaloveit);

1. Ok, so yup, throttle snaps back when not running, lubricated cable, tightened the slack with the adjusting nut on the handlebar. Even tried "twisting the throttle back to idle while running" - no impact.
2. Dismantled carb. Spring, clip, needle valve all in proper alignment, everything looks ok.
3. Manifold o-rings are seatted and look fine, retightened bolts to carb and to block.
4. Assessed carb bowl float, jet and gasket, all looks good. Nothing unusual.

It starts well enough and like I said, can and will maintain idle until I hit the gas, when it won't return to 1800 rpm idle but stays at 4000.

Other air inlets, hmmmm, what about around the idle screw??
Sounds improbable but I think I will try to put some grease or sealant on the threads tomorrow just to see if it makes a difference.
Ran out of daylight today and had to take the last hour off to get in a ride around the neighborhood!

[ChiGongJitsu]

Is your fuel cutoff on the main tank or on reserve?

I've seen a few bikes that act weird when they're on reserve instead of main tank. I don't know if that would explain the braking bringing it back down to the correct idle though.