1988 90hp runs rough

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OK, link length is supposed to be 2.91. My link with it as long as possible is 2.6. So, it can't retard back to 5 deg ATDC thus the high idle. This seems odd since this motor is very low hour, don't think it was messed with but I guess you never know but maybe it was apart and links got switched around.

[TownsendsFJR1300]

Interesting!!

How long have you had this engine?

Did the high idle JUST start acting up?

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Just got it.
I just static timed it 5 ATDC and 22 BTDC and link length is 2.25. I had to break paint seal on adjusting screws. Seems odd how it could be that far out of whack.

I know link lengths are just a baseline but 2.25 vs 2.91 seems like a lot.

Oh well next I'll fire it up and check with a light.

For full advance can I just advance magneto arm without opening throttle? Don't have a test wheel.

Or....just rely on static for full advance?

[TownsendsFJR1300]

IDK know if there's a separate adjustment for WOT timing. See if there's a stopper bolt for the linkage, specifically the advance linkage.

See if it appears that's been dinked with too..

**I would check all THROTTLE, timing advance, etc adjustments in the order per the manual as one is likely dependent on the other.

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Yeah, I "dinked" with both the initial and full advance bolts. Had to break factory paint seals.

[TownsendsFJR1300]

Just got it.

For full advance can I just advance magneto arm without opening throttle? Don't have a test wheel.

Or....just rely on static for full advance?

If you disconnect the carb linkage, I don't see why you can't run the engine to check full advance W/O revving to 8K plus RPMs. You'd just be advancing the timing but no throttles to raise the RPM's..

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Not even concerned about full advance now. Just ran it and 5 deg ATDC and throttles totally closed it runs at 1400.
Could it be spazzed out CDI? Or stator ?
Never seen anything like this.

[99yam40]

if throttle plates are completely closed it has to be getting air from somewhere to run

[TownsendsFJR1300]

+1 ^^^.

You may want to pull the carbs and check to see if the carb to block gaskets are intact / there /installed properly...

A major vacuum leak (no gasket-o ring) would cause the high idle...

[cpostis]

Sounds like classic air leak problem causing a lean condition.

Check your plug colors after your motor has run a few minutes, they should be medium to dark brown. If they are grey or white you are definitely running lean.

Double check your gaskets and sealing surfaces as other have said.

Could be any of the gaskets and or surfaces between the carbs and the block as in the diagram below. Could also be crank seals/o-rings or even the seal between the crankcase halves. See if you find any oil where it does not belong (under flywheel, running down drive shaft, between crankcase halves, etc.)

Some have had success with spraying two stroke oil (messy, others use soapy water with caution a little spritz at a time) around suspect areas a bit at a time. RPM should drop because the oil will temporally seal the leak. Bubbles may even be evident. This could pinpoint where a leak is.

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OK, thanks will do.

[ausnoelm]

An air leak on the engine side of the carb can cause your symptoms.., as can an air leak in the crankcase sometimes cause erratic idle and poor running, but, that said, get your timing fixed first seeing as it's broken.

I guess you failed to read this.....

[TownsendsFJR1300]

You may want to pull the carbs and check to see if the carb to block gaskets are intact / there /installed properly...

A major vacuum leak (no gasket-o ring) would cause the high idle...

or this ^^

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Found the problem. Had wrong magneto link in it. Found a longer one in my box of stuff from part outs. Apparently in 1985-87 they used a 2.13 length link and went to 2.91 in 1988. Threw everything off and wouldn't let carbs close.

Also rough running was caused by #2 plug boot loose. Keeps popping off. Zip tie cured it.
Running great now.

Thanks for replies/help.

[99yam40]

seem that he did not tell us the truth when he said with the throttles totally closed it runs at 1400.

I thought about asking to be sure he looked at the plates to make sure they were completely closed, not just the linkage ,but figured he had looked from what he said.

my mistake

glad to hear you got it going.
who put the wrong link on it?
not many people have a bunch of different parts mixed up when putting together a motor they took apart