1990 Gen 1 - sudden power loss and white exhaust smoke on left side

[C YA JR]

Hi everyone,

got an issue -

Backstory
1. I have a 1990 max, 25k miles now, original motor. bought used in 2000 with. 4k mi. Live in AZ. pic below.
2. sat in garage at one point for 10 years, had it rebuilt jan 2020. jet kit, dale walker holeshot dual exhausts, new plugs etc.
3. ran great until june this year, weekend rides only (100 miles plus) until it got to hot in the summer.
4. Given the age of the bike, and my age, I do not roust on it much. Yeah, I like to drop it down to 2nd or 3rd and snap it to lightspeed, who doesn’t ?

the problem
* This happened in June, when riding it out to my mechanic about 40 min away to replace fork seals.
* I got all the way to my mechanics street, and all of a sudden the bike started losing power, and tufts of white smoke started coming out of the lef exhaust pipe . WTF !?
* my mechanic examined the bike, did compression tests, said all four cylinders were low , see pic - first# is dry, 2nd # is wet testing
* I trust my mechanic, and he freely admits he is a generalist, not an expert on Yamaha. its beyond him at this point.

other than that, the bike is in perfect condition, and was running great. maybe a little slower than 10 years ago, but who isn’t ?

SO - thoughts ? valve seals ? head gaskets? trying to get some direction before I bring it to another shop.

any help would be appreciated - thanks everyone !

 

[one2dmax]

Try putting in a fresh set of plugs to start out with. Keep it simple at first. Likely did not blow a head gasket.

 

[02GF74]

Were you able to identify what the white smoke was?

Could be unburnt fuel or steam?

Have you checked the coolant level in the header tank? If it has gone down and steam was coming out of the left exhaust then I would point at a blown head gasket front left, which has a lower CR than the other cylinders.

Worth pulling the spark plugs out and checking the colour. Apparently a cylinder with blown HG would 'steam clean' the plugs leaving them, well, clean.

 

[Jack Hammer]

White smoke indicates coolant in combustion chamber. Low compression and white coming off like that is unfortunate and most likely means a teardown. You could try radiator leak fix fluids but they are a temp fix at best.

Sounds like a blown head gasket or a crack.

 

[Radioguylogs]

The compression numbers seem suspect- all 4 cylinders are unrealistically low.

Did the mechanic open the throttle while performing the measurements?

The point is, I would follow the advice in post #2.

Make sure there is gas in the gas tank (DAMHIK),

 

[Jack Hammer]

A short video of the bike running would be good.

 

[tvmax]

Other signs of a head gasket could be bubbles in coolant or water in oil or oil is a milky color. They have what is called a co2 sniffer test. It can detect exhaust in the coolant.

 

[Incider]

Other signs of a head gasket could be bubbles in coolant or water in oil or oil is a milky color. They have what is called a co2 sniffer test. It can detect exhaust in the coolant.

We used to put the emissions sniffer at top of radiator tank to help confirm a blown head gasket

 

[3-Max]

I had white smoke from mine recently. It was petrol getting into the exhaust unburnt. Culprit was needle jet unseated & visibly protruding into the carb venturi in conjunction with a literal pile of crap in carb #1. Easy enough to check the needle jet, just take the airbox off & look. You could move it in & out with small flat head screwdriver (It's the brass bit in the pic, shouldn't be able to see this much of it).
I'd also look in the petrol tank & fuel filter for rust, All easy cost free starting points.

 

[C YA JR]

All- thanks so much for all the replies ! I will investigate accordingly and let you know, starting with the spark plugs and coolant levels…I’ll look into getting a video of the bike online as well

 

[cyclejunkie]

Don’t !!!!! Put radiator stop leak in your bike. Yes if it’s blowing white smoke, coolant in the combustion chamber. Sorry to tell you this….but….rebuild.You said in your post”Rebuilt” 2020? Sounds like you need another shop? One that specializes on V-Max. Your dealing with a very specific beast.

 

[C YA JR]

ok gents, been away for a while, time to get my ass in gear. I will get the radiator stop leak, but I will pull the plugs to inspect for build up - they were replaced new in 2020 when I had the engine rebuilt. The bike ran flawlessly right up until it didn‘t. I trust my mechanic, he knows what he knows, but ai am suspect of the compression readings, they just seem all low, but I am not that much if a gearhead to know for sure. i ll post more on Sunday/monday. Thanks for all the suggestions and insights!