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Having a lot of trouble trying to figure this carb tuning stuff out.
History: purchased '97 gp1200 about 3 years ago. Ski came with mild modifications: riva air cleaners, choke removed and primer kit, intake grate, and I believe impeller change. Ski lasted 2 seasons then melted the center piston, siezed the crank.
This year I replaced motor with SBT, and rebuilt carbs.
Carbs were questionable to start out with so I turned all screws in and then back out as per factory spec + over tolerance to assure that mixture should be rich.
Drained all bad gas, put all break-in oil in and filled tank to around 13gal. TCW3 filled into injector tank and stock oil pump tested for normal operation. Basically using old plugs. I've left air cleaners off for testing and tweaking.
Ski is a bit hard to start;. After priming I need to play with throttle to get it going and keep it going for first few seconds. When starting, the motor almost seems like it is unbalanced, but will eventually start and idle. Motor seems to shake a bit, especially around 3000 rpm. Seems to idle OK however if I shut down for more than a few minutes, restart is not as easy as expected.
I've tried "reading the plugs" as suggested on this site, and am just completely confused and frustrated. At idle, my ski makes more smoke than theator fog machine, but the plugs don't seem to tell me anything useful. 3rd looks like it has color, 1st and 2nd are basically bare clean and the seem to stay that way no matter how far I turn the low adjustment out.
Going to full speed for a few seconds turns the plugs clean and white -- a far cry from the nice brown pictures posted in guide. The few times I got it up to speed, it seemed to run well without vibration.
My main concern is melting this engine. I've already polluted the air with about 1/2 tank of gas and am still not sure if it is anywhere even close.
I suspect that I just can't get a good reading with all this oil burning. I also suspect my plugs are fouling from all my low-end testing. At this point I can't be sure if the engine is damaged; it could just not be making power due to being over-rich and fouling.
I think the plugs have to be changed before anything else happens. I'll be compression testing this thing again today.
Few questions:
1) what top-end rpm range should I see on tach?
2) what rpm range is the danger/lean zone for this machine
3) is there any significant difference running with air-cleaners on or off
4) What suggestions do people have?
5) what PSI should I see from a new SBT engine? I think it should be about 125
Right now, my thoughts are to reset all screws to factory spec, not worry about idle/low end, install new fresh plugs, and take it easy and burn up the rest of this gas with the break-in oil. GroupK suggests tweaking lows and highs using an RPM meter and then checking this against plug color and so I might try this.
Any thoughts, pointers, help, references appreciated. Bottom line, I don't want to break this motor and have to go through another re-build, warantee or not.
Thanks all,
History: purchased '97 gp1200 about 3 years ago. Ski came with mild modifications: riva air cleaners, choke removed and primer kit, intake grate, and I believe impeller change. Ski lasted 2 seasons then melted the center piston, siezed the crank.
This year I replaced motor with SBT, and rebuilt carbs.
Carbs were questionable to start out with so I turned all screws in and then back out as per factory spec + over tolerance to assure that mixture should be rich.
Drained all bad gas, put all break-in oil in and filled tank to around 13gal. TCW3 filled into injector tank and stock oil pump tested for normal operation. Basically using old plugs. I've left air cleaners off for testing and tweaking.
Ski is a bit hard to start;. After priming I need to play with throttle to get it going and keep it going for first few seconds. When starting, the motor almost seems like it is unbalanced, but will eventually start and idle. Motor seems to shake a bit, especially around 3000 rpm. Seems to idle OK however if I shut down for more than a few minutes, restart is not as easy as expected.
I've tried "reading the plugs" as suggested on this site, and am just completely confused and frustrated. At idle, my ski makes more smoke than theator fog machine, but the plugs don't seem to tell me anything useful. 3rd looks like it has color, 1st and 2nd are basically bare clean and the seem to stay that way no matter how far I turn the low adjustment out.
Going to full speed for a few seconds turns the plugs clean and white -- a far cry from the nice brown pictures posted in guide. The few times I got it up to speed, it seemed to run well without vibration.
My main concern is melting this engine. I've already polluted the air with about 1/2 tank of gas and am still not sure if it is anywhere even close.
I suspect that I just can't get a good reading with all this oil burning. I also suspect my plugs are fouling from all my low-end testing. At this point I can't be sure if the engine is damaged; it could just not be making power due to being over-rich and fouling.
I think the plugs have to be changed before anything else happens. I'll be compression testing this thing again today.
Few questions:
1) what top-end rpm range should I see on tach?
2) what rpm range is the danger/lean zone for this machine
3) is there any significant difference running with air-cleaners on or off
4) What suggestions do people have?
5) what PSI should I see from a new SBT engine? I think it should be about 125
Right now, my thoughts are to reset all screws to factory spec, not worry about idle/low end, install new fresh plugs, and take it easy and burn up the rest of this gas with the break-in oil. GroupK suggests tweaking lows and highs using an RPM meter and then checking this against plug color and so I might try this.
Any thoughts, pointers, help, references appreciated. Bottom line, I don't want to break this motor and have to go through another re-build, warantee or not.
Thanks all,
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