87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

[grininmonkey]

I just picked up a Bayliner with the 125 on it, made first trip to lake and have some issues. Before taking to lake I checked it out running in the yard with muffs and tried cleaning the carbs and setting the throttle cam link to a point where it would just stay running in neutral as it was cutting off.

During the lake trip, (at first) it was staying cranked at the landing in neutral/just in gear maneuvering away from the landing and a no wake zone.... as soon as I got up to speed, passing the 3000RPM range a very loud noise was happening... below that range it purred and was quite. At WOT, it would maintain for a good few minutes, and then have sudden RPM dips and jumps by 300+/- range and act as it was going to cut off. I stopped and go many times and this behavior was consistent.

It never shut off when throttle was being applied, but after having ran the motor for some time, the idle was way low and would not stay cranked over 30 seconds.. I would restart and if I did not apply throttle in some way.. it would putter and and RPMs just slowly drop and shut off.

At the lake I did the carb idle needle adjustment routine per the manual twice.. to the best of my hearing and the behavior was not improved. I can tell the lower carb responds well to needle adjustment, but the top seems to respond very little. I am worried the seat may be damaged?

Looking over some pages from the shop manuals I came across something that did not make sense. It appears that the throttle cam is suppose to have the arrow (notch markings) centered on the carb throttle roller. The picture shows where it is currently setting.. which is in neutral and the only place it will stay cranked right now. If I do as they say and center the arrow to the roller.. the throttle came will not even touch the roller.

Is there something wrong with the throttle stop, link and throttle cam positions?

How do test/see for certain if the top carb needle seat is bad? (when I took the carb off to clean I could not see in the hole very well)

Could the very loud noise in the mid range RPM be bad fuel mixture due to in correct carb settings or something else?

 

[Jiggz]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

There is something seriously wrong with that motor. First things first. do a compression test. If test is good, you need to correct the problem of idling first even before attempting to run it in the water. A bad idling cannot be corrected by running it in the lake or harbor, instead just makes it worse. Do you have misfiring, most likely. Which cylinder? Have you checked the plugs? Loud noise from where? power head, motor leg or gear box?

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

The noise is more like something vibrating a loud slightly high pitch dinging (after a little bit I was thinking the cowling or something but confirmed is was not that, but did sound like it is coming from the top part of the motor. The motor had power and RPMs were smooth to the point of the WOT issue. I'm not use to these 2-strokes so it's hard for me to hear and say it's miss-firing, the idle sound at the landing was very much the same as another boat next to me with an older mercury 2-stroke... at 1000 to 3000 RPM (cruising speed) it was very quiet and smooth with a nice solid purr or hum to it, so I I don't know enough yet to say... with out getting it professionally checked. I understand the compression test so I'll do that as soon as I can.

First thing I did when I got the boat, was change the plugs, as the owner said he never changed them. When I pulled them out, #1 was the dirtiest, #2,3 and 4 were cleaner but in all, they didn't seem to be in any sort of bad shape.


Would a miss fire problem be constant at any RPM or can it only arise at a certain RPM range?

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

General question, should the idle mixture be set with both carb's throttle shutter completely closed (meaning no advancement of the throttle lever on the carb) ?

I have been trying to adjust the needles with the throttle cam putting just a touch of advancement on the lever, it has been the only way I can keep it running in neutral.

Another question.... adjusting the needle valve should have an effect of increasing or decreasing the idle RPM, correct?

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

View attachment 203711

I just pulled the top carb which was not responding to needle adjustments, when I pulled the float and inlet needle out, green crumbly rubber stuff was falling out. So I unscrewed the fuel fitting and saw more of it in the hole. I can sorta see what I am talking about in the picture. I see a part on ********** for an inlet needle and seat, but it says obsolete. Am I screwed and have a useless carb???

 

[jerryjerry05]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

Pics don't show.
Sent you a pm with my e-mail.
Send me pics.
The parts are all available from different places.
Try Franz Marine.
You do the comp test?
No sense doing anything untill that's done.
The black cam can be turned to align to the marks.
Top post is a procedure from FrankA called a linc and sinc.Do this after the comp test.
Air screws set at 1 turn out from lightly seated.

 

[Frank Acampora]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

I can not get the photo, but the green crumbly stuff will most likely be from the fuel line or tank and it has clogged the carb inlet. You need to clean everything.

NOW: When one carb does not get enough fuel, it is likely that engine damage will occur--especially at or near full throttle. SO: before doing anything, you need to check compression ratio on all four cylinders. The pinging you heard may have been pre-ignition damaging the top pistons.

If all is well and the compression ratio is OK on the top two cylinders, watch the video in the sticky: Tutorial. It shows how to synchronize carbs, carb cam, and timing. You can also read the sticky: Synchronizing timing and carbs.

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

View attachment 203796View attachment 203797

I'll try the image attachment again... but my issue with the top carb was not that no fuel was getting thru, it was that too much was flowing. I had puddles of fuel under the Choke Shutter and down in bottom part of the cowl.. the thing the cowl sits on. The dried up crumbly rubber is the inlet valve rubber. The inlet needle itself had no stopping point.

I can not run the motor at this point, while I try to find a way to replace the inlet valve... so would a cold engine compression test still tell me anything?

By the way... would the best way to pull the pressed inlet valve out be drilling a standard bit to get a grip and pull it out?

 

[Jiggz]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

Well, hopefully, it was more of too much fuel rather than the other way around. You definitely need to rebuild that carb and there are many places you can get parts from. As Jerry mentioned you can PM him if you need locating parts. But don't forget to do the comp test still to verify you are starting on the right foot.

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

I ran a compression test today, however I feel I should mention that the Top Carburetor is off and the bottom is still on. I removed all spark plugs and used a remote starter switch clamped to the starter relay (Red from Battery and Yellow). The following is what I got...

#1 : 140
#2 : 140
#3 : 148
#4 : 136

The bottom two were getting fuel (lubricating) and the top two were not. And this was performed on a cold engine. What is odd to me is the fact that the bottom carb was tunable and had great idle screw adjustment response, but perhaps it was tuned to lean to compensate for the top which was flowing way to much fuel ?

So does my bottom cylinder need inspection (new rings likely) or do you guys think those numbers show it's acceptable as is for a while?

 

[pnwboat]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

What ever you do, don't try pulling that seat out. Replacement pressed in seats are as rare as hens teeth.

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

I had to pull it out.. there was no rubber seal left and virtually useless. I ran across a forum where a tech said he started using Briggs & Stratton part number 394682. It will stick out / protrude more than the OEM, but the float stems can be adjusted to obtain the desired result... allow fuel in until the bowl is full. I don't have much of a choice other than to try it :-(

 

[Jiggz]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

I ran a compression test today, however I feel I should mention that the Top Carburetor is off and the bottom is still on. I removed all spark plugs and used a remote starter switch clamped to the starter relay (Red from Battery and Yellow). The following is what I got...

#1 : 140
#2 : 140
#3 : 148
#4 : 136

The bottom two were getting fuel (lubricating) and the top two were not. And this was performed on a cold engine. What is odd to me is the fact that the bottom carb was tunable and had great idle screw adjustment response, but perhaps it was tuned to lean to compensate for the top which was flowing way to much fuel ?

So does my bottom cylinder need inspection (new rings likely) or do you guys think those numbers show it's acceptable as is for a while?

For now personally, I'll consider these readings within specs. Focus on fixing the carb and then put it together and ran the thing again and see if it runs smooth and then do the compression test again.

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

According to the Clymer Shop Manual, for my motor... #4 is suppose to be the lower than all others and #1 & #4 are are suppose to be between 135-150 and #2 & #3 is 145-160. My #2 was 140, but that was cold and not as lubricated as 3 and 4... Perhaps I should run a treatment or something... The books says as long as there is not a difference greater than 15 among them all, it's ok.

 

[jerryjerry05]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

If the seat was bad and the fuel going everywhere you were getting the fuel in the 2 cylinders.
The draw from the pistons would bring it in.
The compression is right where it's supposed to be.
If my compression was off 15# like the book said,I'd freak. 15# difference is trouble in these motors.
The ethanol probably ate that seat.Some just swell and close off.Some break up.
I think???I have a set of carbs fo a 125/87 They just need the floats and needles from your carbs.
I'll look if your interested.

 

[grininmonkey]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

I would be interested!

 

[jerryjerry05]

Re: 87 Force 125hp (H1251X87B) Carb Issues (Idle,throttle came and WOT sputter)

Going out fishing tomorrow.
The Canaveral Lady.
Will look.Send me an e-mail.
I sent a PM