Was set to do my rings - compression test shook me

chilli

chilli

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So I have the sled all apart, carbs and airbox out, coolant drained...just the block.

I wanted to do a quick compression test for the record, as I am concerned about the outside cylinder, on the clutch side.

Last year, I was consistantly fouling the plug in that cylinder, the other 2 plugs ran sweet all season. I was convinced I was down on compression on that cylinder. I tested all 3, and all 3 cylinders are very close...Not what I was expecting!!

That being said, she's almost at 15,000 KM, and is essentially "virgin" as far as engine goes. She's had Amsoil basically the whole time, and when that plug is working fine, its still a neck breaker as far as speed and accel. goes...

I am obviously going to clean the carbs, but I still need to figure out what the deal is. If I had to bet $$$, id say its the coil/wire/cap on that cylinder. Maybe losing the occasional spark, causing it to foul?


Should I look at changing the 3 coil packs?

I thought that the compression was supposed to vary from one side to the other, does someone have the exact accurate specs?
 
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well, im using an old shitty *** tester, looks like 130s across the board (give or take 1psi) thats what suprised me. I am reading it 130...but the indicator isn't the best. Technically it could be 110 across the board, but again I read it as 130's (hard to explain, but OLD tester...lol)

Regardless of the #, its was the similarity between all 3. Thats whats suprised me.

Thats what makes me thing maybe electrical
 
what do think about my electrical?

I mean, I just replaced the 3 coil packs on my old 1985 Johnson 70HP outboard, and I mean JESUS it was a new motor.

Doing the 3 coil packs can't hurt, but I dont want to spend an arm/leg for something not necessarily REQUIRED.
 
not yet, but reading other posts (symptoms of engine about to blow, step by step engine opening), there seem to be very similar symptoms related to fouling and electrical.

I had to park it early last season, to complete some much needed home renos. When I tried to fire it back up in spring, wouldn't start. Thats why I pulled the carbs...If i poured mixed gas in the cyls, it fired right up.

Once I started tearing into it, thats when I figured Id do my rings too.

Aside from the 1 fouling cyl,,,she still runs amazing... It can foul wihin 10 KM, or after a day of 250+KM, sometimes it doesn't foul at all...it never happens at the same time

Again, this is ONLY on outside cyl, clutch side...
 
For some reason, I'm thinking "check your carb" on that cyl. Make sure your float isnt stuck, the nedle valve doesn't have a slice in it, bent rod, wrong jet size.

Just another avenue to check. Hope you figure it out soon. The snow is flying!
 
May want to replace your plug boots too, i remember reading some members had that problem..could check 'em for resistance too.

anyway now's the time if your freshening things up,hit 'er all
 
chilli said:
so, who's got Part#'s for the coils, wires and boots?

Do they come as a package?
Click to expand...


8DF-82310-00-00 IGNITION COIL(with wire) $34.65

8DF-82370-00-00 PLUG CAP(just the plug boot) $11.97

does not look like the plug wire is re-placeable.
 
coil comes with the wire. Replace all boots its amazing how tight the new ones are.
Cdn price isn't bad for coils.
Stator maybe next, which really isn't that expensive also. MAde a world of differance on my sled.Zinnng
 
I suspect that if the stator was the problem, all plugs would show symptoms.

I think you are doing the right thing, replace the coil and wire, then if you still have problems double check the carb. If that doesn't help, come back here.


As I rack my brain, I also could be convinced that your oil injector for that cyl could be dumping for some reason - check for residue along the intake path.


Keep us posted.
 
Can't say it enough boys get those garbs clean...clean..tear into it...clean it twice...don't just reassemble things...you need to check & see if you got worn parts &/or it is put back together to specs, carbs sync. everything is covered in the tech section...don't do any short cuts...CLEAN THEM CARBS GOOD...cheers
 
theblues said:
Can't say it enough boys get those garbs clean...clean..tear into it...clean it twice...don't just reassemble things...you need to check & see if you got worn parts &/or it is put back together to specs, carbs sync.
Click to expand...
I agree..thats how i work too...
mustangzrule said:
As I rack my brain, I also could be convinced that your oil injector for that cyl could be dumping for some reason - check for residue along the intake path.
Click to expand...
not possible :), oil gets sent to all cyl's equally, oil gets mixed with the gas
in the fuel pump then sent to the carbs..
 
I would go after the cap first - they dont last forever and once they start burning up they go fast.
 
speaking of fuel pump, are there rebuild kits for them?

Can they be tested without the carbs in? I tried turning over the engine with all the hoses disconnected from the carbs, to see if it would spit fuel. I guess without the carbs in, no vacuum = no gas being drawn from tank?
 
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chilli said:
speaking of fuel pump,
Can they be tested without the carbs in?
Click to expand...
yep..get your self a vacuum pump(hand held)attach it to the vac
hose that goes to your case(fuel pump side), pump away...
 
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