Bought some toons, want to swap motors, its gonna be good times!

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
Well what a fun day! Took the toon out on the water with the wife and her friends. Motor ran exactly the same as it did before. So again I cranked all the air bleed mixture screws all the way in to full rich so I could at least keep the motor running while trying to idle around in some spots. Near the end of the day just cruising around 4k rpm motor quits. Restart, hard to keep running, limp into the luckily very close boat landing. Come home and do a compression test, 20psi on cylinder 2, all the rest are 120+. Pull the head and sure nuff, scorched cylinder. So that was fun.


I am curious now. Anyone ever pop the rod cap off threw the intake, pull and replace a piston, and overbore/hone the cylinder with the motor together yet?
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
So that is the plan! Ordered a piston last night, it is .030 but I might turn it down to .020 or even .015 depending how much it takes to get the scoring out of the cylinder. The scoring is pretty shallow so I don't think it will take much. I am going to pop the cap off threw the intake and pull the rod and piston out. I will just use my adjustable sunnen hones to "bore" the cylinder till clean then do a finish hone with the fine stones. I will stuff paper towel in the ports and crank housing to keep metal out while boring. Slap the new piston in and go burn it up again. lol

I do wish I would have done a compression test right off the bat now because I am wondering if that cylinder was weak this whole time causing all my coughing problems. I don't think any other issue cause the scoring as all the other cylinders look great. While the carbs are off (again) I will pull the offending cylinders carb apart and check for any debris just to make sure something didn't cause that hole to lean out.

Thats the plan!
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
I was that close to getting an insurance check for the toon.

haEK9nl.jpg
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
Got home a little earlier today from work. Piston was sitting on the kitchen counter! So I went at it this evening!

The scoring and everything packed with paper towel.

HURKZ8n.jpg


The sunnen set up and ready to start work.

u9tNWeJ.jpg


After only about 50 revolutions of the hone.

3yLFULj.jpg
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
The pistons, old and "new".

tnhNgrZ.jpg


I only had to go .010" deep to get rid of the scoring so I had to take .020" off the piston. The .030" over is thicker than the stock piston by .020-.022". I put the same "ribbed" surface back into the piston.

ARBv5Dv.jpg


Cut the square ring .020" deeper to clear. Also cut the tapered ring groove deeper and a hair wider.

sAxzxEZ.jpg


Rings gapped, rod swapped over (hole facing up) popped in and rod cap torqued to 44ft/lbs.

EJOxfX2.jpg
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
All back together (minus intake side in pic).

1eV4IvQ.jpg


Started it up on the muffs tonight and made all the adjustments again. Running on the muffs with no coughing or popping! Can't wait to try it on the water again!

Taking apart and putting back together the intake was the hardest (most time consuming) thing of the whole deal.
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
Still getting a coughing at low speed/idle. Going to pop the other head off and see what I can see. I may just pull the powerhead and tear it down to figure out whats going on.

By putting my hand over each carb while running I did narrow the coughing mostly down to the lower starboard cylinder but everything on the cylinder checks out when tested. I am wondering if it is the shaft seal since I believe that is the lowest cylinder. I am on edge of buying a complete rebuild kit and just do it all if I am going to tear it down. All new pistons and rings, new seals and gaskets, the whole bit. I am in it to make this one a good one! lol
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Have you eliminated the carb as being suspect? Have you balanced the carbs using vacuum gauges to make sure they are pulling equally? Balance can cause the issue pretty easily.

I had to go through the Honda 90's carbs AGAIN (3rd time) to get them right. Never did see the issue as I was going through them that time. Same symptom, occasional cough and stall on idle. Now we can idle around at 800 rpm for hours.....
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
Been breaking in the new piston/rings. lol

H4My2r4.jpg



STILL I am getting coughing. :( I can dial it out at idle now with the mixtures screws but from slight throttle input (1100rpm) to around 1800rpm is when I get the coughing. Above 1800 it runs great, and at idle it runs alright.

I am still suspecting the lower starboard side cylinder as the cougher. I plan to swap around carbs to see if the problem follows the carb. If it does there must be a crack int eh carb I can't see, or something else is going on with it I can't figure out. I will then buy a replacement carb and give that a try. At this point I do hope the problem follows the carb.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Are you running a healthy dose of Sea Foam though it? That stuff is expensive when you run at high dosage, but I've seen it "fix" more than one carb....
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
I haven't. I have been threw the carbs multiple times and everything is super squeaky clean. I am thinking if there is something wrong with a carb it might have a crack or something I can't see.
 

weaverunner

Cadet
Joined
Aug 26, 2017
Messages
13
I would keep a close eye on your plugs and do a compression test frequently since you have not yet determined what caused the #2 piston to let go.

Do you still have all of your idle mixture screws set 3/4 turn out? If so, something is not right. Do you have your float height adjusted correctly? I believe the service manual calls for 2-1/2 - 3 full revolutions out and adjust in 1/8 turn increments.
 
Last edited:

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
Yes the idle mixture screws are still all around 3/4 out. I may be able to turn one or two of them out a bit more. I have adjusted the floats, a couple times even, they are spot on according to the book.

I have to figure out if that one carb is bad in some way then replace it, then see what sort of adjustments I can make to the rest of the carbs.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
I think you have that backwards. You should do what you can to adjust the carbs, and if they don't respond as desired, THEN replace one/them.

The carb "sync" process, where you adjust throttle openings to make sure all are supporting the engine equally using a vacuum gauge (or a cluster of them to allow you to monitor all at once, highly preferred!) - I haven't seen where you've tried this yet - and it could easily be the root of your issue.
 

weaverunner

Cadet
Joined
Aug 26, 2017
Messages
13
Try pushing in the key in to activate the primer solenoid during the low speed miss and if it clears out, most likely you've got a clogged low speed jet in one or more of your carbs.

Any white deposits on your spark plug electrodes or any variations in color?
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
I think you have that backwards. You should do what you can to adjust the carbs, and if they don't respond as desired, THEN replace one/them.

The carb "sync" process, where you adjust throttle openings to make sure all are supporting the engine equally using a vacuum gauge (or a cluster of them to allow you to monitor all at once, highly preferred!) - I haven't seen where you've tried this yet - and it could easily be the root of your issue.

From what I read the plates can't be adjusted from top to bottom (one side) but can be synced from side to side (one side to the other). I have done that every time I took the carbs off and put them back on again, about 4 times now. I haven't use a vacuum gauge, just the paper and light threw the plates. I do have a vacuum gauge though, I can try running it and move the gauge around to see what I can see that way.

As far as adjustments go I have made every single one many of times. I started over and did everything by the book multiple times. Somehow not enough fuel or to much air is getting into the lower starboard side cylinder.
 

snowseeker

Petty Officer 3rd Class
Joined
Nov 1, 2004
Messages
93
Try pushing in the key in to activate the primer solenoid during the low speed miss and if it clears out, most likely you've got a clogged low speed jet in one or more of your carbs.

Any white deposits on your spark plug electrodes or any variations in color?

Yes and yes it does in fact clear up for a little while. That is actually what I have to do many times to get away from the dock and to where I can apply some throttle. At least now when warm I am able to idle around somewhat but I have the air bleed on the lower starboard side cylinder turned all the way rich to do that. I have had all the carbs completely stripped and blew out with the compressor multiple times. I feel I am missing a hair line crack somewhere in the offending carb.

The plugs looked good and even last I looked and at them but I am not sure if a lean idle would show up on plugs unless I idled (or tried to) the engine for a good amount of time?
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
As far as the need to hit the choke a few times on a cold start, that's not REAL unusual. My Honda is like that. Takes it a good 10 minutes to settle down. When cold, they're looking for a richer mixture to run right. OR, there's a chance the process you're using is when adjusting is leaving the idle mixture too lean.
 
Top