glowing Exhaust/ backfiring in exhaust Help!!!!

[Imech9]

Just got a xmoto xb-31

Assembly was good, and everything seemed fine,

It started on the first kick, but after a few minutes the front pipe was glowing and if you reved it, it backfires in the exhaust and the pipe glows
more.

I AM SCARED I AM GOING TO HEART THE ENGINE!!!

Any Ideas I tried changing the main jet to a 92.5 from a 100 that it had and I think it made it worst.

I put the 100 back and tryed changing the needle position it seem to be best wear it was 2 above bottem.

I am in Toronto Ontario so we are at about 400 feet above sea level.

I just don't know maybe too lean???

The other question is why would changing the needle position adjust change the why the pipe glows at idle because I thought this circuit was not in use yet. The idle, I would bet would be at like 800-1000 rpm.

I thought through the ad when I bought it that it was supposed to have a Mikuni carb on it and now going through it I find it has a K & F carb that is supposed to be made by Mikuni??

THIS SUCKS!!

Any Help would sinerialy appriciated

Thanks Mark

[warrior91]

Absolutley too lean . :(
I would diagnose a leak in your intake... if not check exhaust header/cyl. fitment and tightness of nuts.

[knothead]

Absolutley too lean . :(
I would diagnose a leak in your intake... if not check exhaust header/cyl. fitment and tightness of nuts.

^^^what he said, plus make sure you have the top of your carb screwed on straight and all the way, a little loose can make a big difference.... and make sure the rubber boot where the cable goes into the carb is in place.

[Imech9]

Hi

Ya could be I rightened the nuts on the intake maifold but you kow i did not see a gasket, its going into work tommorow.

This is killing me!!!!

I had the top of the carb off 10 times I think I got it on striaght and tight.

You know when I had the carb off and I chaged to main jet to 92.5 I did adjust the idle mixture from two turns to 1/1/4 and it ran worst .

Who came up with this placement of an adjuster screw, its treable, whos got a flat screw driver bit and tough figures to adjust lean best idle??

Don't get me wrong I love the bike!! I had a hard time getting the jets,
no body wants to sell you large round mikuni jets for a china bike!!

And those jets are wrong didn't look like large mkuni jets fit though??

What jets does a K & F carb take??

Thanks Mark

[ejcycles]

Mark
Post a picture of the carburetor or send me a pic to my e~mail in my signature. K&F who knows unless we have a picture. Not many of the 200cc bikes use Mikuni Carburetors.
Mikuni & Keihin carburetors both make aftermarket carburetors, there are even some companies that copy both. The Jets from these carburetors are not interchangeable... as for the fuel hole size. They may fit but it doesn't mean that they are correct.

[kelly5150]

I don't think the glowing red part of this issue is anything to concern yourself with . I have the Viva model of this bike, cheap thin pipe is the issue there . The backfiring is the crappy carb and smog crap on it. Delete both and am sure it will run right-er .
I have mine tuned to where the carbon build on the plug is right, but it still builds up in the pipe and spits a small backfire in the pipe as it warms up, I attribute this to crappy carb, too much smog crap .
My pipe has glowed at idle from day one, I worried about it for awhile but my burn is right as rain on the plug, so it AINT TO LEAN freinds . It's a thin crappy header and a bad carburetor, which none of these China carbs are all that great, even the so-called Mikuni copies from Japan .
The carb idle screw position on that carb sucks , yes, yes it does on a perimeter style frame. You'll need to braze on an extension so you can reach up there to adjust that easier . This bike has its shortcummings with the stock carb, but it is a very nice riding bike. If your worried about intake leaks, shoot some WD-40 around the intake when its running. If it changes idle, it has a leak, if not, it doesn't , PERIOD !
Red pipes are nothing to worry about anyway, they are supposed to get hot, its a motor . I can light a cigarette off my Harley or Norton or Viva bikes when I ride . Don't lick the pipe and you shouldn't have any problems.

Hope this helps, Cheers, Kelly5150

[kelly5150]

One more thing ?
Have you ever rode a fast street bike at night ?
Look down at your header when your getting on it hard, it glows redder than China !
Why do you think the chrome on most bikes turns blue man ? Blue , red, orange, thats heat signature man. With the actual fire that emminates in the cyclinder and spits into your pipe, it is supposed to be hot . Try that at night sometime and you'll be amazed how hot motors get , let alone pipes .
Also, tapp on your pipe on the XB and you'll see that it is mighty thin steel compaired to allot of pipes . I also don't think the expansion chamber is big enough in the header either on this bike ? May be some of the backfire issue too, especially with the smog crap on it too .

Cheers, Kelly

[Imech9]

Hi

You know running it up and down the street it feels good.

I have to find the digital camera, my daughter had it so give me a bit to post some carb bike pics.

Its just the backfiring and glowing parts that are unnerving.

I have a friend I work with that used to race gp bikes, he set up the carbs
on my sled with good success.

I will let everyone know how it goes.

THANKS FOR ALL THE HELP!!!

Thanks Mark

Gio/x-moto xb-31 250cc

[IronFist]

Hey Brother:
I live near Kipling and lakeshore in toronto. Soon as the weather hits and my bike is set up I can skoot out and see your chinabike. Is it going street legal? Too bad I sold my chinabike before I got the chance to go on a chinaride with someone else. :( If you don't mind riding alongside a honda let me know. N2r. Pull your sparkplugs and tell us the color on the electrodes if you haven't already done so.

[Imech9]

Hi all

You guys have been like great with all the ideas.

O.K. I didn't relize it but the hose to the deceleration valve mounted at the steering head was melted against the top of the cyl head.

I didn't see this untill it was on the trailer to go to work, a little higher and not looking down on it i guess is why i didn't see it.

With the hose fixed there is very little back firing.

I like the horny sound of the exhaust but wow is it loud, I had people coming out of the show room to see what it was.

I took the exhaust can apart, and the packing is loose, but hey its there
and a spark arrester wow thats cool.

trying to get the bolts back in thats another story, I guess they are one time use, should be self tapping stainless.

SO TO FINISH!!!

I fixed the hose, got ride of the backfiring, adjusted the needle clip down one slot (now at the bottem slot)

Gave it back to brien(friend at work who raced gp bikes)

He takes it out into the hydro field (WOW DO YOU THINK I SHOULD HAVE TOLD HIM ABOUT IT NOT HAVING A RIM LOCK ON THE REAR WHEEL???)


Thats O.K. he found out, brings me a bike with a flat tire and pieces of rubber hanging out the rear rim.

I guess the jetting is closer. Oh and I had to bring the forks up in the triple clamps because he thought it felt like a chopper. (.5 of an inch)

Now we are at 400 feet above sea level, We should come up with a basic jetting chart for these engines based on sea level.

Or would it be a problem with the variation in the brands of carbs mikuni
or K&F???

So at this point it still a llitle, lean Brien has needs a number off of the needle to get one with a better profile and we may be changing the main jet from a 100 to something a little richer.

This was the first time i really got to ride it a bit its got a lot of pull down low.

the prior bikes i had we all older two strokes( like ten years ago)

we are both mechanics at saturn, but bikes and carbs are very old to me.

so its cool to adjust it and see the changes as you go you know.

I will keep you up to date.

Thanks Mark

[Imech9]

Well so far so good have yet to get a tube and rim band and a wheel lock
will go to gp bikes tomorow to order it.

I just noticed a oil leak at the left hand case seam???

is this normal/NOT!!!
What know??
will have to take the cover off on saturday to see why has any one seen this??

Thanks Mark