120 looper got a cough

[redshad]

Hello Ive got a 1990 120 looper that I rebuilt and it has a little cough at idle. Just a bit of history I originally broke a seal ring and totaled the power head. I found one on Ebay and put in some new seal rings and one new piston and all new piston rings. Took it out for a run and it ran great but seems to have a cough (blowback thru carb) It kinda of sounds like this (bo bo bo bo bo Puff!! bo bo bo bo bo Puff !! ) and I see a puff comming from the air box when at idle. I pulled one carb down to inspect and it looked prety clean so I didnt pull the others apart. Right now Im thinking maybe carb kits are in need due to them sitting up for a few years. Any thoughts Is it OK to run it like this or should I wait
Thanks

 

[redshad]

Re: 120 looper got a cough

One more note to add. I did empty all th old gas and put in new

 

[Faztbullet]

Re: 120 looper got a cough

You need to repair before using any more, this could be a carb running lean from being dirty, a damaged reed valve or block, a ignition problem which any which may have caused old motor to fail....

 

[redshad]

Re: 120 looper got a cough

10-4 I pulled the plugs out on the side that was puffing from the carb and one seem to have some hard material that flaked off the plug my first thought was crap is that aluminum but I could crush it with my fingernail, so I think it was carbon build up. Is this a sign of that carb running lean? Ive only ran it for about 10 min in the water between 3 to 4k RPM after the rebuild. Do you think I should pull the head off to inspect the cylinder?

 

[71Windsor]

Re: 120 looper got a cough

Lean carb just had the same exact symptom. Spray each passage through until the spray comes out evenly and smoothly. I took a peice of 80lb test line and went through each passage as well to ensure I got it all.

 

[redshad]

Re: 120 looper got a cough

OK 71Windsor thanks for the info. I just got done breaking down all the carbs and cleaning them real good. All the orfices seem to be clear. I soaked all the jets and metal parts in some barrymans carb cleaner for a few minutes. I will put it all back together and try it again. Did you buy rebuild kits?

 

[redshad]

Re: 120 looper got a cough

Update. I cleaned and reinstalled all the carbs and throtle body. Put it on the hose and same thing at Idle I get a puff blowback around the carb area. I began removing the plug wires one at a time and found the puff goes away while I have #3 unhooked. As soon as I hook the plug wire back up ans start up the puff is back. So the problem is common to #3 cylinder and carb. What should I do next? Im going to go ahead and put carb kits in. Also I checked the compression on #3 135 PSI
Hers a vshort video of the Puff

 

[redshad]

Re: 120 looper got a cough

Inserted a short video of the Puff Any Ideas?

 

[daselbee]

Re: 120 looper got a cough

not #3, it is #4 carb that is sneezing. lowest one in the stack, #4.

on loopers of this family, the carbs are on the opposite side of the cyl they feed.

clean the idle circuits in the throttle body. they are behind that welch plug about the size of a dime.

 

[71Windsor]

Re: 120 looper got a cough

x2 with daselbee

 

[redshad]

Re: 120 looper got a cough

OK Thanks Do you think the throttle body is causing the issue. While I had it apart I cleaned the throttle body and blew air thru the idle circuits and they appeared to be clear.

 

[71Windsor]

Re: 120 looper got a cough

Air would move through the passage pretty well even with a obstruction you will have to physically check its tedious

 

[daselbee]

Re: 120 looper got a cough

OK Thanks Do you think the throttle body is causing the issue. While I had it apart I cleaned the throttle body and blew air thru the idle circuits and they appeared to be clear.

Looking into the calibration pocket in the throttle body, how big were the holes down in the bottom?

If this is baffling to you, you missed the most important part.

 

[redshad]

Re: 120 looper got a cough

Ok Im going to pull the throtle body back off and get more detailed checking them. I just think maybe its in the throtle body. The carbs looked super clean. Do you know of a liquid cleaner that I can spray into the throtle body ports to clean them ?

 

[redshad]

Re: 120 looper got a cough

Im thinking you are talking about the holes three or four in a row I cant remember but it goes from a larger hole to a smaller hole. Im guessing about the size of a # 2 pencil lead is the largest hole going smaller.

 

[redshad]

Re: 120 looper got a cough

Is there a difference in the new part # 0439079 vs old part# 0398557 for the carb rebuild? I was wandering is the newer version compatable with the ethenol and the old not?

 

[daselbee]

Re: 120 looper got a cough

Im thinking you are talking about the holes three or four in a row I cant remember but it goes from a larger hole to a smaller hole. Im guessing about the size of a # 2 pencil lead is the largest hole going smaller.

The holes are very tiny, maybe 5 thousands in diameter. They are behind the round welch plugs.
They pass thru to the throttle bore right at the throttle butterfly.

Try this...you may get lucky. Get a can of spray carb cleaner with a straw. Put the straw in the front of the carb, directly into the brass idle air bleed jet. With engine running, spray. The cleaner will run thru the idle fuel circuit directly, and may dissolve anything that may be in there.

Use the whole can on four carbs.

 

[redshad]

Re: 120 looper got a cough

Update on the Looper. I done just as daselbee said and got Lucky. One thing I did differant also was run the motor in a drum of water instead of the hose. I got just a couple of puffs then I let it run for a bout 15 minutes and clean as a whistle. Carbs seem to settle in with no leaks also. I think its ready for the river. any body know about what temp the head should be at when running?
here is a short video

 

[redshad]

Re: 120 looper got a cough

Thanks for all the replies and help
Redshad

 

[Bosunsmate]

Re: 120 looper got a cough

You should be able to keep you hand on the heads, so not higher than 160ish farienheit.
If thats idle rpm, seems quite high