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  #1  
Old 09-27-2002, 07:09 AM
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Default \'89 Quadzilla jetting

About a week ago I picked up an '89 LT500 from the original owner. It is original right down to the tires, chain and sprockets. The problem is the guy iced raced it occasionally (I also got a full set of studded tires, plus paddles), and I think that was the last thing he did with it, meaning I don't think it ever got re-jetted to warm weather specs. It is slobbery rich, from idle all the way up. Does anyone know the stock jetting for this beast? Also, I do most of my work on snowmobiles, and up until now only on roundslide carbs. If the internals of this Mikuni flatslide are different, give it to me in shirtsleeve english so I don't get lost. Thanks in advance!

Bob
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  #2  
Old 09-27-2002, 03:47 PM
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Default Re: \'89 Quadzilla jetting

Tthe 88-90 were stock 350 main jets on the Mikuni tM38ss carb with spares 340 and 360 . The 87 was a stock 420 main with spares 380 400 and a 440 for the Mikuni TM38SS.
Also for the 89 -The jet needle is a 6dk3-3rd and the needle jet was a R-2
The pilot Jet is a 22.5.
Now remember this is all for a STOCK 89 quadzilla
It also suggests turning the air screw 1-1/2 turns back
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Old 09-28-2002, 09:31 PM
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Default Re: \'89 Quadzilla jetting

Hmmm, now I've got some investigating to do. All the jetting checks out as stock, except for the air screw, which was out 2-1/4. It ACTED like it was rich, but in fact it is not. I found some crud in the bowl drain plug, so it may have been sucking some of that in the main at WOT, and there was more crud in the needle and seat area, so the bowl might not have been filling right. Put it together, still not right. Kind of a dull, droning sound at idle, lots of popping and loading up when revving it up. I'm thinking water, which makes me think head gasket, and I understand these things are known for that. I'll check that tomorrow. Thanks for the info.

Bob
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Old 09-28-2002, 09:38 PM
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Default Re: \'89 Quadzilla jetting

How are you mixing your gas.....(ratio?)
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Old 09-29-2002, 08:05 AM
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Default Re: \'89 Quadzilla jetting

I've only had it a week, and it still has the gas in it that the other guy put in. The stuff in the carb looked pretty clear when I drained it, so I ran some out of the petcock into a jar and it was pretty clear too. It sure doesn't look like the 20:1 they recommend. But it smokes (blue) a lot more than I'm used to, and it's spitting quite a bit of oil around the pipe at the motor. I was thinking I'd better drain it and start from fresh. Is it safe to go leaner on the oil in these, like 24:1 or 32:1? What about the exhaust valves on these, do they ever get buggered up? On my sleds they are pressure activated and they get gummed up with oil goo and carbon occasionally and need to be cleaned. I understand these are gear driven mechanical, so they should be pretty reliable. (?)
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Old 09-30-2002, 06:35 AM
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Default Re: \'89 Quadzilla jetting

I mix 32:1 . i like to play it safe ....i dont need to blow mine up. I do understand that it will get carboned up a bit but thats why you have to stay on the pipe and clear it out. Sounds like you might have a cracked ring but i cant be sure. How's the compression when your kicking it over? Does it start easilly ? Also Make sure to check the reeds for chips or cracks if you havent allready done so. Let me know if new gas does the job...
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Old 09-30-2002, 11:22 AM
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Default Re: \'89 Quadzilla jetting

I pulled the head, gasket is fine. Pulled the carb again. I found all the stock jets (main, NJ, pilot) in there when I first checked, so I took for granted the needle was right. Wrong. Right needle, one clip too high. When I had the head off, the piston top was washed clean from raw fuel. I've cleaned the (stock) air filter, both layers. Tried it with the outer layer off, and the box lid off, no better. My leg is killing me from kicking it, it's got every ounce of compression it should have. I think it's just too heavy on oil, with the oil slowing down combustion to the point of leaving unburned fuel.
On a related note: what plug should this have? It had a Champion N4C in it, which I think is equivalent to an NGK B7ES. I don't have any B7's, so I've been trying B8's and B9's.
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Old 09-30-2002, 03:06 PM
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Default Re: \'89 Quadzilla jetting

your fuel mixture shouldnt affect it that much..could the choke be stuck on [img]images/graemlins/confused.gif[/img]
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  #9  
Old 10-01-2002, 03:36 PM
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Default Re: \'89 Quadzilla jetting

standard plug is a B8EGV
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Old 10-05-2002, 09:34 PM
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Default Re: \'89 Quadzilla jetting

She's rockin' now. I checked the choke. Looked OK, but it seems to click a little better when I flip it now, so something may have been wrong there. I can't believe I didn't think of that. I dropped the needle one more clip and put a B8EGV in it ($7.00!?) and it's a WHOLE lot better. It's still a little fat at WOT, so I think I'm gonna put the needle back where it belongs and drop the main down to a 340. Thanks for the help guys!
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