I will start by saying I have googled it ALOT and have yet to find an answer.

1987 It will die at idle everytime I start it. If I give it gas it will usually die, occasionally it will get up to 5k or so and then it will bog there again. Warm or cold.

I cleaned the carbs twice using a total of 3 cans of carb cleaner. I was very VERY thorough.

What works is if I adjust the throttle stop screw till it idles at 2500rpms. Then it will go to 11-12k, but im not to sure its a good thing to idle that high, just to avoid the real problem.

Thanks

 

Did you disassemble the carbs and clean them that way or spray through them without opening them up? It still sounds like you have a carb issue to me, either not being clean or not being synched properly..

Not exactly sure why cranking up the idle speed makes it rev higher at the moment, but you are correct in the thought that it's only covering up the issue.

If you leave the choke on does it run better or worse when it's warmed up?

 

Make sure it is firing on all four cylinders. I spray water on the header to check if all the cylinders are running. It is easy to identify which one is dead if it doesn't evaporate immediately. Then you can trouble shoot the correct one. Pull the plug. See if it is wet or dry or all carboned up. Inspect the exhaust for dings.
It sounds like you need to clean the low speed jets in the carb.

 

I disassembled them completely 3 times now and the last I soaked them overnight in parts cleaner. It doesn't make to much of a difference choke on or off, the dead spot from 3k to 6k is still there. And now it won't go over 8k. I am going to try to sync them this weekend. I made something to sync them and tried to use it last weekend, but it didn't read anything at all, so I guess there was a leak in my lines... I did also unscrew the main and slow jet screws and cleaned them. Also unscrewed the float bolts and cleaned those and the filters.

Can one or two of the choke ports being slightly open constantly cause strage effects? Like richening just those one or two cylinders. I noticed it the first time I pulled them apart, but figured it was normal?
Thanks for the replies!

 

Okay, So! I checked to see if each header was hot and the far right one is cold. So i'm thinking burnt valves, but I don't have the right fitting to test compression. The intake sucks air and the exhaust blows it out, that's all I was able to find out. Plugs are wet when I pull them. Spark is good and it's hooked up correctly. Coil resistance is fine and dandy.

How long do head rebuilds usually take? I can't imagine more than a couple hours...? Ive only done Subaru head rebuilds. And it seems pretty straight forward and easy on a motorcycle. If it isn't the rings, what all should I be replacing/doing kit wise? Would it be easier to just buy a used engine that works.... like a fuel injected one 8), or just another F engine. Would an F2 or F3 work?
Thanks

Good/hot 3


The cold one

 

Start with the simple stuff. Try a new plug...wet and carboned up could be a fouled plug.

 

I bought new plugs and put them in already, but just to make sure it wasn't the plug I swapped it with a plug that was in it before. Just to triple check that both aren't bad I will swap one from a running cylinder. Is there any other littlw thimgs I can check? It has strong spark and I don't see anything wrong with the wire. I could swap a wire too...

 

Suck squeeze bang blow. Air filter clean? Compression? Fuel, good quality gas making it to the combustion chamber and being metered correctly. Spark...strong and delivered to the correct cylinder. Plugs tight. Exhaust...inspect that it is clear.
I bought a parts bike that both the air cleaner and exhaust was packed with pellets of dog food, seeds, and mouse turds. It wasn't pretty. After cleaning the air filter, i had to crank the bike over and over. It had spark but it was acting like it was flooded. I opened the throttle to give it one more try and BOOM!!!! I guess enough air and fuel made it in. It blew the obstruction out of the exhaust and plastered the siding on the house with dog food, seeds, and smouldering mouse turds. That was not a fun stain to get off the siding.

 

I'd sync the carbs. If not that you can always locate the jets on the far right cylinder and blow air threw the passages of the carb to the intake just to make sure nothing is clogging or blocking it. I believe even if 1 cylinder is not firing the revs should still go up. I had that happen to my bike once but I don't remember much about why it happened. Good Luck

 

Okay so I did a compression test and it was 110,105,95,110. Cold..
I have discover it is fuel. If I spray starting fluid in the dead cylinder the header heats right up and it idles/revs perfectly. I guess I will clean the carbs again, but I think it might take something more than that. I will drain that specific bowl to see if it even has gas. That's about as far as I know how to look.