Ironhead Mikuni 38mm - Page 8

bigbadgun · #71 13th February 2012

I really think PinionGear should be paid from Mikuni for all the PR he is doing.

piniongear · #72 13th February 2012

Quote:

Originally Posted by pitbovver

I have the large o-ring style with the airplane style Stainless Steel clamps. My front head has a small chip out of the lip on the intake, but i felt a smooth transition between the intake manifold and the head and it actually went together very smoothly as compared to the SS intake manifold/orings etc....
Again, i am stumped. If i squirt ether in there it has "fuel", I verified it has spark, and it is making compression on the "thumb in the hole test"

Are you certain you have the engine on the compression stroke (both valves closed) when the slash mark is dead center in the inspection hole?

I am sure you do but I have to ask anyway.
Back firing through the carb sounds like the timing is not correct and that makes me think it is too advanced.
Backfiring can also be the result of an air leak at the manifold.
Are you sure the small chip is not causing an air leak.
You may want to wrap electrical tape fully over that clamp where the chip is to seal off any leak that may be there.
If the engine starts after doing that, then there is a problem at the chip area.

I don't have a lot of hope that may be a problem but it pays to eliminate the possibility.
I am currently trying to load a video on You Tube explaining the Mikuni Pilot System which is the area of the carb relating to starting the engine.
There are a few things that may (or may not) be of help to you or another member.
I will continue to try to come up with some remedy for your problem.
Meanwhile please take a good look at your ignition system and the engine timing.

I will post the video later after it loads on You Tube.
I think it will be 2 videos because it is over 15 minutes in length and that requires almost 3 hours to get them loaded for viewing.
pg

piniongear · #73 13th February 2012

Quote:

Originally Posted by bigbadgun

I really think PinionGear should be paid from Mikuni for all the PR he is doing.

Now that would be nice indeed!
But I tout the Mikuni as much as I do because I have found it to be absolutely best carb anyone could hang on an ironhead.

I am a true believer in the Mikuni only because in 1973 I could not get my bike started with that damn Tillotson carb that came on the bike when it was new.
The Mikuni fixed that problem with a single kick and ever since that day I try to give some help to others who have starting problems.
99% of the time a Mikuni is the answer.

And what ironhead does not have starting problems at one time or another?
pg

pitbovver · #74 14th February 2012

i will reconfirm my timing (aint gonna hurt) its possible it may be 180 out but i did go through the sequence via the manual (just as you described) and it came up on the timing mark when the test light went out. Maybe i got lucky the last time i statically timed it but i do not have the mark on the body of my dizzy (not sure where it came from) but it did work last time and ran fairly well, starting consistantly so I would say that the o-rings should be sealing sufficiently.
The only thing that happened to start this whole process was that it died on its own like it started to lose power during the previous round of heat cycling. Is it possible something else happened?, I guess anything is possible....It would be so nice if it had a starter, I am positive with a bit more revolutions this thing would start...Any ideas on getting this thing on a wheel starter or something similar?

piniongear · #75 15th February 2012

I strongly suggest you recheck the timing making sure the flywheel mark comes to the inspection hole on the compression stroke (when both valves are closed).

It is easy to miss this and have the timing mark lined up in the hole but the flywheel is on the overlap stroke instead of the compression stroke. So check that again.

I think you are having another problem (rather than carb problems) and yes, an electric starter would be nice at this time but you will be able to get your bike tuned to the point where one single kick is going to light it off.

Installing a Mikuni is the best step toward achieving that goal that you could take.
Let us know how the timing looks when you get it checked out.
pg

lucky23 · #76 15th February 2012

Quote:

It is easy to miss this and have the timing mark lined up in the hole but the flywheel is on the overlap stroke instead of the compression stroke. So check that again.

Hmmm, I wonder if thats my problem?

pitbovver · #77 15th February 2012

thanks for the vote of confidence. I have succumb to the flu, and my knee is playing catch up. Maybe tommorrow, but then there is snow on the ground (soubt that would stop me...HeHe)

piniongear · #78 15th February 2012

Quote:

Originally Posted by lucky23

Hmmm, I wonder if thats my problem?

If you have any doubt at all, then it is something you need to check.
Easy to do this and then that possibility will be eliminated from the list of potential problems.
pg

pitbovver · #79 16th February 2012

well looking into all the recent mikuni activity spearned me on to trying different techniques for shits and giggles. This led me to see fuel was dripping from my rear cylinder @ the exhaust port. I knew it had been leaking there before but i shrugged it off as an exh leak. Well i kicked it over by hand and looked with my other hand and it appears as i have blown out my head gasket?! could this be my problem? guess i should have done that compression check after all...time to dig out the leak down tester....

fdny37 · #80 16th February 2012

Yes, I think a blown head gasket is definitely your biggest problem.