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1988 9.9 No High end - STUMPED

V

vtrider22

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Help! I have a beautiful/pristine J10RCCD that runs better than any 2-stroke I've ever owned, here's the catch, up to about 30-40% load. It idles better than some 4-strokes! BUT If given full throttle it will shoot right out great and then within 1-1.5 seconds drops back to what feels like a lean misfire. If I keep it there at WOT, after 5-7 seconds it will pick up and GO! But only for a second, then goes into a FULL - NOTHING -FULL - NOTHING thrashing. If I madly pump the ball I can intermittently get it to stay up at full power. My obvious first thought - lean. Went though carb - same result - went through carb again - same result. Replaced the fuel pump - same result - swapped fuel tanks -same result - checked the hoses/fittings all the way through - found no issues. With help of friend with outboard "addiction" - swapped coils - wires - power pack - same result. At this point I'm questioning vacuum - could it be leaking at the upper/lower crank seals? I also question the reeds. Could they cause this type of symptom?
Yes - I've kind-of backed it up to the parts dept but clearly failed. Ideas? STUMPED
 
Yep... what Boobie said.

Also... check the pin/socket connections within those small rubber connection plugs as they have a habit of backing out resulting in poor connections.

Plugs should be Champion QL77JC4 plugs gaped at either .030 (long life) or .040 (hot spark).
 
joereeves said:
Yep... what Boobie said.

Also... check the pin/socket connections within those small rubber connection plugs as they have a habit of backing out resulting in poor connections.

Plugs should be Champion QL77JC4 plugs gaped at either .030 (long life) or .040 (hot spark).
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Thanks guys, Totally not the way I've been going. ........ I think I sold my timing light years ago..........
 
I believe there are 2 different ignition systems on that motor depending on when it was made. One will have the module under the flywheel, the other style is bolted to the head by the spark plugs. If you have the module under they flywheel look at where the wires exit the stator assembly. You are looking for worn wires they are known for that. That module is also not the most durable.
 
flyingscott said:
I believe there are 2 different ignition systems on that motor depending on when it was made. One will have the module under the flywheel, the other style is bolted to the head by the spark plugs. If you have the module under they flywheel look at where the wires exit the stator assembly. You are looking for worn wires they are known for that. That module is also not the most durable.
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Being there is 12" of ice on the lake I did a bench test of the complete ignition system whilst spinning the engine at significant RPM with a drill. Plugs are the correct ones and appear in great shape. No carbon tracing found. I was able to get both plugs to jump an arc of the gap (.030) plus about 3/4" to a ground screw. The arcs were good and hot up to about 1/2" where they got spindly. This was the only way I could figure to do a "loaded" ignition test. Thoughts about results of test? My conclusion was - Pass, Ok, Good.
This is the style with the power pack/module bolted to the head by the plugs.
 
vtrider22 said:
Being there is 12" of ice on the lake I did a bench test of the complete ignition system whilst spinning the engine at significant RPM with a drill.
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How long did you spin the engine like this? I really hope you somehow sprayed down the internal bearings and cylinder walls with fogging oil, 2-stroke, or at least some kind of lubricant.

KJ
 
vtrider22 said:
If I madly pump the ball I can intermittently get it to stay up at full power. ...Went though carb - same result - went through carb again - same result.
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If it speeds up with the bulb then it is a fuel issue no?

What does "Went though carb" entail in detail?

I think your high speed jet has a clog. If it was me, I'd take the carb apart and spray all the orifices, specially the high speed jet with CRC Isopropyl Alcohol Precision Cleaner through the red straw that comes with it (Isopropyl alcohol does not harm the carb like some carb cleaners).

image_201328.jpg
 
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kevinj said:
How long did you spin the engine like this? I really hope you somehow sprayed down the internal bearings and cylinder walls with fogging oil, 2-stroke, or at least some kind of lubricant.

KJ
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Only 3-5 seconds each cylinder with a cordless drill not on full throttle. Not like I wound it up full tilt.
 
Klink, that's exactly my thought process. I figured for sure that the "main" jet in the bottom of the little "bucket" had junk in it. First teardown it got a full carb kit and cleaning with appropriate chemicals ( I own a german car repair shop, used to dirty kooky crap). Second teardown of the carb was to make sure I didn't miss something. It is absolutely perfect from what I can see. I swapped out the fuel pump with a brand new one as I was not satisfied I had gotten that little prick back together right. The tank&hose swap was more of a sanity check than anything. The really odd thing about this issue is it is very consistent. Generally that's exactly how I like broken things (cars) to come in the door. This fault happens EXACTLY the same way every time. Pulls out of the hole like champ for a second or so then feels like it runs out of full fuel flow. The fact that it comes back for a second a few seconds down the line just muddles up the whole thing even more.
I generally don't post to the "phone a friend" forums like this but this one's really got me on the ropes.
 
I had a similar problem with a 25hp Kawasaki lawnmower engine and was asked by a mechanic on a forum if I had sprayed each orifice with the straw till I saw the spray coming out the other end the same as it comes out of the straw. I told him I hadn't, and he said it must be done, that just dunking a carb in cleaner does not always do it. I had to take everything apart (radiator and more) for the third time to get to the carb (radiator and more) and did as he said, and it fixed the problem. In that case, the lawn mower would run perfect for as much as a 1/2 hour, then would start to backfire, I would then slow down and do something or other, then it would run well again for 15 minutes and I was done with the mowing. I lived with it like that while trying different remedies as time went by (carb, new fuel pump, going through the ignition system), till I discovered the carb spray technique. I have been using it on outboards every since. Make sure the spray pattern comes out of the orifice the same as it comes out of the straw, indicating that there is nothing restricting it. In the case of the lawnmower, you could see there was a restriction and the spray could not dissolve it out, so I used a hair from a brass brush I had and tit got it, then I sprayed to clean it.
 
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Klink said:
I had a similar problem with a 25hp Kawasaki lawnmower engine and was asked by a mechanic on a forum if I had sprayed each orifice with the straw till I saw the spray coming out the other end the same as it comes out of the straw. I told him I hadn't, and he said it must be done, that just dunking a carb in cleaner does not always do it. I had to take everything apart (radiator and more) for the third time to get to the carb (radiator and more) and did as he said, and it fixed the problem. In that case, the lawn mower would run perfect for as much as a 1/2 hour, then would start to backfire, I would then slow down and do something or other, then it would run well again for 15 minutes and I was done with the mowing. I lived with it like that while trying different remedies as time went by (carb, new fuel pump, going through the ignition system), till I discovered the carb spray technique. I have been using it on outboards every since. Make sure the spray pattern comes out of the orifice the same as it comes out of the straw, indicating that there is nothing restricting it. In the case of the lawnmower, you could see there was a restriction and the spray could not dissolve it out, so I used a hair from a brass brush I had and tit got it, then I sprayed to clean it.
Click to expand...

Thanks Klink - I'll give it a try - anything sounds good at this point SL
 
flyingscott said:
Is the throttle roller in good condition and not falling apart.
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Yes, the roller looks great and is adjusted correctly with contact being just made by the "little vertical casting" - for lack of a better description.
I've run it on the boat with the cover off and verified the t-linkage wasn't getting fouled up somehow.
 
Yes, after putting a rebuild kit in the original and test driving ( ran the same) I did throw a new one at it - for no gain once again.
 
Lots of good advice by others but you gloss over "checking the fuel hose". Being a '88 it predates alcohol blended fuels wide use. You could
have a delaminated hose liner that is collapsing when the fuel pump tries. Using the primer bulb will force the liner to open and pass fuel.
I also have seen the liners crumble to pieces in some of the newer hoses and form a dam at the fuel hose end connector of liner chips. Again the primer build can force fuel pass it but the fuel pump pull it past. Another observation is you mentioned the lake frozen over. So your use must be seasonal rather than year round. The shelf life of these new blended fuels is only about 90 days, after that they start to go bad. So your fuel hose is full of rotting fuel for all the months you don't use it. Just some thoughts I hope help.
 
Pull the fuel line off the carb and pump the primer bulb. Do you get a free flow of fuel to the carb? My guess is a plugged quick connect at the motor where the tank connects?
 
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