Need advice 89' 340cc Exell 3

My good freinds got a real bad bog when running his sled. When it's warmed up and at idle 1,000 rpm you hit the throttle and it bogs and stalls out. If you half choke it then you can get past 3,000 rpm to engage clutch to get going. Guess carbs need cleaning and adjustment? Looks like they have never been taken off. She does have great upper top end just no bottom end to get going. Guys have any tips on what to look at?

I did this also this morning....

Checked the spark plugs. Light tan brown colour but the BR9ES are not the solid caps. Going to get new ones and gap them to spec. Anyone know the spark gap for them?

Also did compresion test. And motor cylinder #1 is 119 psi and cylinder #2 is 120 psi. What should it be if it was new? Just wondering.

I told him not to go and spend $90 an hour to tune it up. He's got 3 kids at home and money should be spent on family. This should be a easy fix I hope. Told him we will take the carb off there's only 1 anyways. And get her all cleaned up in my garage. They look all black from dirt over the years.

Anyways any tips on jetting or tunning is greatly appreciated. Vince my freind has been a great friend to me over the years. I want to see his kids enjoy the little Yamaha this winter with no headaches.

Talk to you soon guys...

RDL

Rej, CLEAN that carb !!!!!!!!! If it revs up with the choke on pilot jets are most likely blocked off ....

I' ve got a factory service manual for my Excell III out in the trailer. I'll go dig it out and post some stuff later tonight.

Shark

Dean,

Rej, CLEAN that carb !!!!!!!!! If it revs up with the choke on pilot jets are most likely blocked off ....

Click to expand...

I'll be sure to clean the carb out good. Will let you know on how the pilot jets looked like. My buddy is taking the carb off the sled and will be over later tonight. Will see how dirty they are. I got lots of carb cleaner waiting to go to work!

Mark,

I' ve got a factory service manual for my Excell III out in the trailer. I'll go dig it out and post some stuff later tonight.

Shark

Click to expand...

Thanks for checking your manual for me. I'll get back to you later on what it's got for jetting.

Rejean - Are you sure it's an '89 Excell III? The reason I ask is that the only 340's for 1989 listed on the Yamaha Parts Catalog website are Ovations.

Anyway, I have a service manual #LIT-12618-00-45 for my 1983. It lists the carburetor as B38-34 Mikuni
I.D. Mark: 8T600 or 8J600
Main Jet at sea level: #240 -30C to +10C
Main jet to 600m: #240 up to 0C #220 -10C to past +20C
Main jet to 1200m: #240 up to -20C #220 -30C to +10C
Pilot Jet: #75
Pilot screw: 1.0 turns out
Throttle valve: #190
Valve seat: 1.5mm
Float height: 25mm plus/minus 1mm
Slow adjuster screw: 1.5 turns out (Top right side of carburetor if you're sitting on the machine looking forward)
Engine Idle speed: 1,700rpm plus/minus 100rpm (Maybe it's idling too slow to start with?)
Spark plug: BR9ES
Spark plug gap: .7-.8mm

Some other stuff that you might try:
Starter Cable Adjustment: Pull the starter cable outer tube upward, and adjust the free play between the outer tube end and adjuster to 1.5mm-2.5mm by turning the adjuster. After the adjustment, tighten the lock nut and replace the rubber cap to keep the lock nut free from dust and water.

The thumb throttle control should have .5mm-1.0mm free play at idle (between the thumb throttle control and the throttle cable guide that's welded to the handlebars)

My Excell III ran great when I bought it. It would top out at 60-70mph, which was plenty fast for my daughters. Then one year it was a total dog. It might get to 30mph at full throttle. Sometimes I would start it and the engine would run forward, sometimes it would run backward. It was pretty funny to see the sled going in reverse! It turned out that the CDI was bad. The engine ended up seizing because the Yamaha dealer didn't put the oil injection line back on after tearing the engine apart. I transplanted another 340 into it a couple of seasons ago. There's no way to squirt gas in the carb with the air box on, so I drilled a hole in the airbox and routed a rubber tube down into the carb and rubber cemented it to the airbox so that I could squirt gas into the carb on those hard-to-start days.

There's some other stuff in the manual about tuning the carb that has pictures. I can scan the pages and email them to you if you need them. Like I said, this is for my '83 340cc, but I imagine that there weren't too many changes from year to year.

Shark

I just scanned the carb section and sent it to your yahoo email address. Should have done that in the first place.

Shark

Thanks for your help guys....

Well look at how dirty the carb cleaner is at the bottom of the orange bin. Was pretty bad inside and out. My buddy is doing the cleaning in the photo. Dean you were right she was pretty pluged up. We took everything appart and used 2 cans of carb cleaner. Blew out all the holes with air. Now you can see it's going to run better. Tomorow it should be back on the sled to test it out.

I'll get back to you guys on how it runs. Thanks again Mark and Dean for the advice

Here's a after photo...

That looks better !!! LOL