Help with my yamaha moto 4 200

[stuartyamaha]

Hi all,
I am new to this forum so please be gentle lol.

I have a yamaha moto 4 yfm200.

It starts great, but misses and back fires when hold a stead rpm. If you gun it it will also bog down and stall.

I have stripped the carb out and cleaned everything, but still the same. I have also put a new plug in and changed the oil.

The carb on mine is a Mikuni VM22SH - INU00

I have read that the pilot screw has to come out 2 turns, but are there any other setting that i need to know about.

Regards
Stuart

 

[Painthehouse]

Valve timing off?

 

[stuartyamaha]

I dont think my valve timing is off, as i had a friend strip the engine down, as the gearbox had disintegrated. He put a new tensioner on, chain, rebuilt gearbox ect ect, and he is really good at what he does over here in the uk, and he checked all that when he rebuilt it.

Regards
Stuart

 

[Painthehouse]

From what I know the only reason it could be back firing would be if their was a valve problem. That'd cause misfiring too.

Was it running good before?

 

[stuartyamaha]

Its always done this from what i can remember. Is it easy to check the valve timing, as i am a novice with these

 

[Painthehouse]

Here's the 2 part manual, should give troubleshooting and specs details.

ATV Yamaha YFM200 YFM225 Moto 4 200 225 Clymer Service Manuall - Free Download from rapidshare - FilesTube.com

 

[stuartyamaha]

Thank you very much for that link. That is very helpful indeed. I have a new air filter coming from yamaha. When i get that I will then check everything with regards to the manual and see how i get on.

Regards
Stuart

 

[Braaaptor]

Ignition coil!! First thing I'd replace. Period. This is an older ATV and I've had the exact same problem with a Moto4 220 I rebuilt a couple years ago. The igntion coil can gradually break down (years of vibration doesn't help matters any either) and leave you with intermittent spark. Get a replacement coil, put it on, and I bet your problem will go away.

 

[2g00d4u]

my moto4 200 was a piece of sh*t, I ended up replacing the entire electrical system.

The coil getting weak might be a problem also, that's what made mine run awful

 

[stuartyamaha]

Thank you for your help guys.
Can anybody recommend the best place to buy the ignition coil from then, as i dont want to keep on going to yamaha, as there expensive over here.
Any help would be appreciated.

Regards
Stuart

 

[Painthehouse]

Check through these.

yfm200 ignition coil | eBay