Crossfire 150 idles but then dies...
 

Hey all,

New to the forum but I've read every post on carb, electrical and valve problems.

History is that I bought the crossfire 150r for x-mas off Craigslist. It's ran great until last week. While my 8 year old was riding it one Saturday it died and was really hard to restart. Finally got it started and it backfired and wouldn't stay running. So..after reading all the posts..here is what I have done so far:

1. Cleaned carb. It wasn't very dirty at all.

2. Adjusted both valves to .004. Intake was at zero so some improvement there.

3. Replaced spark plug.

I have not tried replacing the coil or other electronic parts yet.

Now it starts fine but as soon as you step on the gas it dies.

Ok so what do you guys think?

Update-and a new problem.
 

Ok, dump simple error. I took the spring loaded top off the carb and the needle insert was not fully engaged downward where the needle seats into the main jet...duh. Must have happened when I cleaned the carb and put it back together. Now it runs as before.

But now that I've read all these posts..it's not running right yet. Does not go completely to WOT top speed. It sputters and backfires a bit at full throttle.

Also, when running especially under heavy load, it feels like the chain "skips" every 5-10 seconds. Almost like you had just run over something. Is that the CVT having an issue?

I'm completely new to the CVT concept.

Eliminate
 

First, welcome to the forum. as for the backfiring/sputtering, I'd check the carb to make sure you have it adjusted right, you could be just that 1/4 turn off on the jet or pilot! also make sure your intake is all tight and you're not sucking air somewhere. As for the "slipage" check your chain, is it worn, does it need tighten, or are either of your sprockets showing excessive wear? hope this helps you some. anyone else:dunno:

Thanks Bear,

I'm going to pull the chain and make sure I don't have a frozen link. It looks pretty good but maybe its out of alignment on the shaft and skips every now and then?

You also may have an air leak in ur pipe connection if not the intake, if chain and sprocket is ok check ur belt may be slipping.

Welcome to the site. When you say backfire, out the carb or out the muffler?

Make sure your chain has only 1/2 - 3/4" slack at the tightest point on the chain. Also look for that "frozen link" too.

The backfire is out of the muffler. It just seems like it wont rev up to the limit when you try to go wide open. It struggles a bit

on or off?
 

Is the backfire under acceleration, or when you lift off?

Welcome to the forum 3boys. I have nothing to add, you are in good hands.

That's actually a very good question. ^^^^^


Your boy was driving and it just quit? Nothing else to it? Ran out of gas, hit a tree, did a 360, etc...

Has your temperature changed drastically since then?

Any mods done since?

What's your compression?

Can you do a plug chop? Run WOT and hit the kill switch. Then remove the plug and look at the color. Black = too much fuel, tan = perfect, white = lack of fuel (dangerous)

Do you have access to another coil just to try for testing purposes? Sometimes elec is disguised as a fuel issue. Esp at high RPM.

Nothing happened at all other than the fact that he had been running it for about an hour. Since then, I have adjusted the valves (the intake was essentially at 0) replaced the plug and cleaned the carb.

It runs now as it did when i bought it, but I notice now after reading many posts on this forum that it is not running all that well.

The plug is a little too black and oily so its running rich. I'm going to adjust the mixture today when I get home from work.

I was thinking about buying the better coil and maybe a 30 MM carb and rejetting. So the question is whether the cheap Ebay carbs are ok to buy?

It sounds like a lack of compression. If one valve was set to 0 and it was run at WOT this could cause a valve to tap the piston and get a slight bend (ask bear he's dealing with that now) best way to find out without tear down is a compression test. Are you certain that the timing was at top dead center when you lashed the valves??

Yes, I watched the now famous youtube video 3 times and made extra sure. I'm going to stop by the auto parts store and get a compression gauge today and check it. What is the compression supposed to be?

I sure hope the valve isnt bent...but it would be a great chance to rebuild the top end...hmmm

I think most are around 140psi. Someone else who knows for sure will chime in soon. That's the way to be positive about a possible bent valve. If your valves are properly lashed and your compression is low odds are there is valve damage.Does it smoke bad or did you notice excess oil on the plug when you changed it? This could be a sign of bad rings which also causes lose of compression. If none of that then the cam timing could have skipped a tooth. In any case its best not to run it more than needed to diagnose until you figure it out as the possibility for greater damage is pretty high. If you have to tear it down you could go ahead and get a port and polish done on the head....BIG difference to power.

Slestak is correct. Need that compression test for sure.

Black and oily plug? Might have another issue going on. Don't start buying performance parts just yet.

Compression is normally around 150ish. Prob don't want to be any lower than 125 I would think.

Top end rebuild is a piece of cake! really starting to enjoy tearing into these engines!

Ok, so I started it up to bring it up to the garage from my shed to work on it today and it starts backfiring like crazy. I notice that every time it does, the lights go out and then come back on. Is this an indication of an electrical problem? Coil?

It's running rich from the looks of the plug.

What doesn't make sense it that after I fixed the error I made reassembling the carb, the thing ran pretty well. I'd say 85%. Started right up. Idled well. Certainly rideable. Today? It would hardly stay running with a lot of backfiring. So the problem comes and goes...

That's why I'm wondering about electrical. Maybe the auto choke?

Gremlins!

http://www.google.com/url?sa=t&sourc...LIue0xQFBRvYOw

Here is an article with some info on the auto choke and how to test.

Update. So I removed the stock air box and replaced with a UNI. The plug was switched to the NGK instead of the autolite. Guess what? It runs great...really great. Absolutely purs..

My kids have been riding it it now for 2 hours...

I wish it made sense, but I'll take it. Now onto the chain issue...

The autolite plug was the wrong plug since they do not make a plug for the GY6. Glad you found the problem

Ditto!!!

SWEET!!!!! Hate it when your puzzled but gotta love an easy fix.

Well...not out of the woods yet. So they rode it yesterday for 2 hours. Then again today for 2 more. All of the sudden it starts to backfire and sputter then dies and it won't restart.

Now I'm really confused. Electrical issue or bad valve or head issue?

Only seems to do it after its hot....

Thoughts?

In order to know which direction to look, a compression test is really the next step. Start it cold and see if it runs. Turn it off and check comp. Then ride it till it starts backfiring and repeat

Have you ever checked the valve adjustment? Might be time.

polarity
 

May not be it, but try reversing ur sparkplug coil wires, it might be backwards ur polarity that is.or you might of bought a bad sparkplug coil...Eddie.

Well u got 3 good tips to start with!

Are you getting a good blue spark, are you getting fuel. When it quits and won't start those should be the first 2 things you check. Until you know those 2 things you'll be shooting in the dark.

Always start with the basics!