98 Vmax 600 twin

H

Hockeyman

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St. Clements, MB
Trying to dial in my father’s sled...

It’s a 600 twin that he rebuilt after oil pump failure and overheating.

Original plugs before oil pump adjustment:
957874B4-B919-42C1-B381-CA9024878491.jpg

Same plugs after 160 Kms on trails:
066D65A7-FE41-480D-9631-F8DADF4D9386.jpg

Think I’m headed the right direction but still a little too much oil, used about 32 oz of oil over the 160kms. Used roughy the same fuel as my father in law’s 2019 Polaris 800 as our pump fills were 22.5 +/- litres each after 100kms of trails.

Should I expect much more out of this 600 once I dial the oil pump in better?
 
Do the math. 32 Oz is 946 liter of oil

22.5 L / 0.946 = 23.8

So your burning 23.8 to 1 fuel / oil mix ratio That's very RIch.

Ideally you'd want something closer to 50:1
 
Last edited:
Vincent said:
Do the math. 32 Oz is 946 liter of oil

22.5 L / 0.946 = 23.8

So your burning 23.8 to 1 fuel / oil mix ratio That's very RIch.

Ideally you'd want something closer to 50:1
Click to expand...

Unfortunately those numbers don't quite reflect a correct mixture as I added the oil after 160km (at home) and fueled up at 100kms. Next trip I will fuel up and add oil at the same times and keep better track to see where the ratio is at.

To me the plugs look like it's still too much oil. Will turn down pump some more and take it back out on the trails for another 100 kms and see how they look.
 
A couple of bucks said:
There is a gas/oil ratio calculator in this thread.
https://totallyamaha.net/showthread.php/70243-oil-pump-gap-23-5-mm?highlight=Calculator
A general rule of thumb is 1qt: 1 tankful of fuel.
Have you adjusted the pig rich needles yet? (Easy peasy)
Click to expand...

Haven't touched the carbs yet... Has no issues with fuel delivery that I notice. Was a bit surprised that a 2019 800 burn roughly the same fuel as a 98 600.

Will probably pull carbs this upcoming summer and go over them and rebuild. Figured I'd dial oil pump in first with the current carb setup then do it again next season after carb rebuild.
 
One other thing I do notice is that it is a PITA to start if it sits in the garage for over a week. I Usually pour some fuel oil mix down cylinders and then its one pull and I'm not worn out from pulling on the cord trying to get it started...

If used less than 7 days +/- its usually two or three pulls and it starts.

Definitely need to buy a sled for myself with electric start so the trails can wear me out and not starting the sled! LOL
 
Hockeyman said:
One other thing I do notice is that it is a PITA to start if it sits in the garage for over a week. I Usually pour some fuel oil mix down cylinders and then its one pull and I'm not worn out from pulling on the cord trying to get it started...

If used less than 7 days +/- its usually two or three pulls and it starts.

Definitely need to buy a sled for myself with electric start so the trails can wear me out and not starting the sled! LOL
Click to expand...

The fuel pumps weaken with age. What I have done instead of buying new pump is install boat-type primer pump between tank and pump(the line that goes over the airbox bracket. This works great.
As for rich running, on a sled of this age you need to buy new main nozzles from Yamaha, part number 8AY-14141-56-00. They wear out.
Also be sure to inspect the oil pump drive, as these also wear out sometimes and can cause engine failure if it rounds off completely.
 
Hockeyman said:
Unfortunately those numbers don't quite reflect a correct mixture as I added the oil after 160km (at home) and fueled up at 100kms. Next trip I will fuel up and add oil at the same times and keep better track to see where the ratio is at.

To me the plugs look like it's still too much oil. Will turn down pump some more and take it back out on the trails for another 100 kms and see how they look.
Click to expand...

I absolutely wouldn't try to read the plugs to figure out and set oil consumption, that just isn't going to work. When the oiler fails it goes to wide open oiling so yes the plugs will look better after a new oiler is put in, but you won't be able to read the burn on them and correctly set the oil ratio. For all you know the oil ratio could be too little and the carbs are simply jetted rich and causing the plugs to be that dark brown.
Do the math like Vincent showed to determine ratio after filling both fuel and oil up and riding for a while. Get the ratio correct and then do some runs to determine how jetting looks per the plugs or looking down the holes at the top of the cylinders.

For your hard starting issue, when you pull the carbs during the off season check that the choke plungers are fully opening and working correctly.
 
If I used 22.5L of fuel over 100km would equate to 10.45 mpg. What's average consumption for trail conditions?

Also, if I added 32 oz after 160km using the average of 4.44Km per L gives a ratio of 38:1 rich.

Adjusted the pump so at wot the marks are parallel with lines touching.

I came across a pro action video on YouTube and then went to look over sled in the garage. The rear weight transfer rods are missing the bottom nylon spacer, washer and bolt on both sides... Must have vibrated loose? Or I never noticed they weren't there. Guess I'll have to head to the Yamaha dealer to see if they stock them or other alternative suggestions anyone here may have.
 
Sounds like you're on the right track.
Just wanted to make sure you weren't adjusting the oil ratio simply by reading the plugs. It does sound like you can adjust the oiler down a bit and check again.
I don't know what average fuel mileage is, but to get jetting correct I would get the oil ratio dialed in and then do plug checks.
 
That’s the plan... dial back oil until it’s near the 50:1, then this summer pull the carbs and rebuild. Once carbs rebuilt then I’ll be tuning the sled all over again. Thankfully there’s an empty field across from my place to do plug chops.
 
10 mpg is pretty good for a 600 twin.

are the oil pump marks lining up by the recoil at wot? had 500 twin and that was how it was checked.
 
Maim said:
10 mpg is pretty good for a 600 twin.

are the oil pump marks lining up by the recoil at wot? had 500 twin and that was how it was checked.
Click to expand...

Yes, marks "should" line up at wot. I have mine set just before the mark but still slightly touching and it's still too rich. Will probably end up with a small 1-2mm gap once I hit 50:1

I would imagine the type of oil used can also affect pump setting... Dad has always used Shell oil so that's what I've kept adding back.
 
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