Weird low rpm problem

[dbeardslee]

Don - I missed it on Erics, but you just gave me the idea I was looking for. Thanks, brother.

[dbeardslee]

I think I found the problem.

Pete - I rebuilt the heads and lapped the valves about a year and a half ago, so I'm reasonably certain there's nothing wrong there. Besides, I just pulled the carb boots, and every one of the gasket surfaces had gasoline on them - a pretty sure sign they were leaking. Now I'm weighing my options - whether to cut more gaskets and double up on them, or just use some high temp gasket sealant. My experience with gaskets has been that doubling them up is not always a good idea, so I'll probably use the gasket sealant - won't use much as the last thing I want to have happen is for that stuff to squeeze out on the inside and then get sucked into the combustion chamber.

[Ivan]

Gaskets between rubber and aluminum aren't that great of an idea, IMHO. I used Permatex Aviation Form-a-gasket Type a (the hardening type). It is fuel resistant, silicone is not. It is also inexpensive. I have never had a problem with them leaking for over 20k miles.

All that being said, I would check the valves. If you lapped them, and have run them for a while, chances are you need to set them again. The symptoms you describe are all pointing to that. The face and seat of the valve wears, and the clearance :€ss€0s. So always err on the side of a wider gap when steeing valves, not a closer gap. Its not that tough to just check the lash on this bike, and it would either confirm or eliminate a possibility. The valve cover is a good place to use high temp silicone. IMHO it works better than a paper gasket.

Good luck on finding your trouble.

[DiverRay]

I used Permatex Aviation Form-a-gasket Type a (the hardening type)

I use the Yamabond #4 on most sealing surfaces on the bike. It will NOT dry, so it will flex a little as things heat and cool. John posted that the thermostat gasket from a Ford 2.3l engine is the same bolt pattern. Four of those and a little Yamabond and you should be good to go.

[dbeardslee]

Ivan - I'm really not worried about the valves. I set the clearances at the top end of spec with valve wear-in in mind when I did the head and it hasn't been that many miles since I did it. And like I said, gasoline on the gasket surface is a pretty clear indication of a leak there. I'm going to use some permatex ultra grey on 'em and see how it works - it's recommended for intake manifolds, which is basically what I'm working with. Yamabond is also a good idea, but as I've already got the permatex... Also going to fab a bracket to help support the carbs.

[bikerphil]

I always use the Ford 2.3L thermostat housing gaskets as mentioned above with some Yamabond or similar. Never had any problems.

[egleaves]

Doug, Eric had one on his bike, did you see that one? Went to two of the screws in the brace across the four carbs and then up to I think where the air box used to bolt up to the frame IIRC.

That's how it was set up when I bought it, I thought that bracket belonged there!

It works great. I back out two of the little Philips screws there on the carb rail and the whole bracket swings completely out of the way.

I'll get a picture of it when I get home and post it here.

[dbeardslee]

I've been wrenching on Betsy most of the day, and just got through installing a gleaves bracket (tm, Eric Gleaves). Everything's back on, except for the tank and seat which I'm not going to put back on 'till tomorrow morning. If I do it now I'll never make it to the end of the cure time on the permatex without firing it up .

Here's where I think I made my mistakes. First was not having a gleaves bracket installed. Second was installing gaskets on the hangers in the first place. The fiche doesn't show gaskets, and there's a little rubber seal on the end of the hanger anyway - and besides, they weren't leaking that way. And lastly, not checking the torque on the hanger bolts every time I had the carbs off with the gleavesless setup. They weren't as tight as they could/should have been. Not loose, but still...

Of course I still haven't verified definitively that leaking carb boots were the problem - but I'm pretty sure of it - hense my issues with cure times . I'll post back in the a.m. and let you know what happens.

[egleaves]

I've been wrenching on Betsy most of the day, and just got through installing a gleaves bracket (tm, Eric Gleaves).

I wish I could take credit for it, but as far as I'm concerned it's a PO Bracket. The one on my bike is so well made that I just assumed it was supposed to be there. Looks factory to me.

[dbeardslee]

Alexander Graham Bell didn't have any trouble with the concept. Trade mark that sucker, says I .

[boyat68]

Double check the band clamps on the front boots to see if one of them are cocked. This may cause the boot to open up a bit during riding due to the vibration and weight of the carbs.

[dbeardslee]

Well the suspense was too much for me so I put her back together and fired her up. She ran better, and the synch gauges were behaving nicely, so that was good. Then she started acting up again - not as bad as before, but still not right. Then I noticed something else - a lot of oil around the lower right front of the bike. Looks like maybe the galley plug o-ring wants to be replaced. There was quite a bit of oil, and it started me wondering. What happens if you soak the generator in oil? Could these problems be related?

Ivan - I take it back - it has been that many miles since I lapped the valves. I just checked my maintenance book, and I'm right at 6000 miles, so they're due for a look see too.

[petejw]

Just thought id throw something else out there,
have you checked your pick up coil gap,
ive just gone into mine, the gap was the size of
a sparkplug gap, after resetting, the bike is running much better, especially down low.

[dbeardslee]

I gapped the pickup coils at .56 mm right after the head rebuild last spring - a little close but I wanted it that way with those old magnets.

Here's the weird thing, it runs OK when I first start it in the morning. It gets warm enough to take it off choke, and it will still run OK for maybe 10 minutes. Then it gets finicky at idle. Before I removed the hanger gaskets and applied the permatex, it wouldn't idle for more than a few seconds, and the synch gauges were doing all kinds of weird stuff. Now it's idling, and the synch gauges are behaving nicely. It's just got this low rpm miss. Even warmed up, it runs strong once it gets past 3k, which usually indicates a pilot circuit issue.

As I'm pretty well positive I was getting some air leaking past the boots, I suppose it's possible that the last time I colortuned I was compensating for the extra air getting into the mixture which would cause it to be rich once the air leak was stopped.

The last time I washed it (two weeks ago) I must have gotten something wet, and it acted a lot like it's acting now. Whatever got wet dried out and it was fine for several hundred miles, and it hasn't been in the rain, but the symptoms are awfully similar. Then there's the issue with this newly found oil leak, which seems to be coming from the galley plug - haven't verified it yet, but that's the next thing on the list to fix. I don't know if an oil soaked generator could be causing the problem, but I know something isn't right there, and experience has shown me to fix the stuff you know is broke first.

I'm still sceptical that the valves would be causing the problem. Stop me if I'm wrong, but if it was the valves wearing in the onset of the problem would have been gradual and it wasn't. It was running perfect one minute, I heard a little 'poot' and several minutes later it started running like crap at idle.
Could the little poot have been the galley plug o-ring letting go, and could that cause this problem?

[petejw]

ive set mine at .004" (.102mm) and when i searched on
here that was a recomended setting, mine was set
at .024" (.610mm). This adj alone has made a big difference especially down low and mid range.

if the problem becomes worse when the engine warms up
it usually indicates a rich mixture.
maybe lean the mixture screws in half a turn.

if you have the colourtune plug are you able to run the engine at the rpm where the problem is and see what colour you have?