1989 Yamaha Bravo
 

I picked up an '89 Bravo the other day with just under 2500km. I somewhat know the history of the machine and don't have any reason to believe it's a lemon or anything. It wouldn't be much of a loss if it was given the price. Anyway, we drug it out of a cold sea can yesterday and after a few primes it started effortlessly. The issue I'm having is it won't take throttle without dying right away. I can get the revs right up there if I prime it ever so slightly while staying on the throttle. I believe there's some sort of fuel issue here, and I'm hopeful that a good carb cleaning, particularly the idle or pilot jet will fix the issue. She really seems to want to go but something is starving the engine of fuel - at least that's my guess.

Any past experience/tips on this would be appreciated. These old machines can be great units but I know they can also be finicky at times...

Could b the pump

1.How old is the gas,
2.any fuel filter,
3.Could be junk in the float bowel or jets, they're easy to clog,
4.pump diaphram may have pin holes,

Any of this is a cheap fix, start with easy stuff. How long has the sled sat since it had a good run?

Probably since this time last year. There wasn't much fuel in it so we dumped 5 liters or so in. Also added some gasoline antifreeze last night but not much changed.

Take your carb apart and seafom all the pieces needle jets slide. You’ll probably find a difference. Those old machine are pretty basic and reliable.

BW

Do you have a heated shop or garage to let it sit in? Would eliminate the condensation somewhat, when stored near empty they can get a surprising amount of water build up.

Take the carb apart and make sure it’s good. A jet could be clogged, the floats or float needles could be stuck. Take all the jets out and run a wire through them to clean them out, spray isn’t always enough.

CLean the carbs for sure. I’d actually drain the gas completely. Mix a new batch and see how it goes.

Love those old bravos.

Part 2...
 

So the initial problem was solved with a thorough carb cleaning and the sled has since started flawlessly and will idle all day.

What I have been finding recently is that the machine will run fine for about 3-5 minutes after a cold start, but then starts to bog down when I’m on the throttle. It will putt along at about 20-30 km/hr but any more throttle and it really bogs down to the point of not going anywhere, but the engine still fights to stay alive. Adding a bit of choke kills it outright. I have changed the spark plug and the problem persists. I’m wondering if it is a belt issue, and once that belt heats up after sitting all night it stretches out and effects the clutching. Thoughts?

X2. Main jet plugged. Main jet controls rpm from mid to top. Clean.

How long have you tried running it for and how cold was it outside?

Had same issue a while ago. Sled sat for years in a barn covered with a tarp and had not been started in approximately 8 years. Found that crank seal behind clutch was dried out and cracked sucking air thru it. Pulled motor and clutch myself and installed new seal. Seal is pressed in but with a little patience had seal in place. Run like brand new for kids. Still using sled.

Not sure if that year had any electric throttle override safety feature, but I've had sleds where that has been the issue, and is easily mistaken for a fuel problem.

I put about 10-12 km on it yesterday with this issue. It was about -5 to -10. Like I said it just plods along at 20km . I could barely get enough revs to engage the clutches by the end of that, but it idles just fine.

How did you figure out it was the seal? I can’t really see in there.

I was given my friends older sled after he passed. Same issue, ran great with some quick start, not on it's own. Two carb dismantles, soaking everything, a good clean and runs tip top now. Drain any fuel, add some sea-foam and new premium to start after you get those carbs cleaned.

Well I didnt read far enough DOH. Belts don't stretch, they fall apart of give off stringy hair like stuff when they wear out, could be a clutch issue but I think your issue is still fuel related. Fuel pump could be your next check. Cracked fuel line, sucking air?

What’s odd is that it runs like it should when I start it cold, like in the morning. She’ll rip for about a mile then she just wants less and less throttle. It was running awesome after the carb clean around Christmas and then this after sitting outside for most of January and February.

I would check the carb again, some crud could have flaked off and plugged a jet or something.

Carbs need cleaning just went through that w/my machine, also check those carb boots if they have them, could be an air leak

Closure!
 

Turns out we were all wrong. I stopped in at TNT Power Sports in
Bonneville and had their mechanic look at it. In about 30 minutes he determined that there was a loose connection between two wires connecting the stator to everything else, essentially causing weak spark. Simple fix but I would have never figured that out. I hope this helps someone else down the road.