Tuning Update

[mack]

Well setting the float height to 26.2 from 25.7 did nothing for the stumble at 155-3000 rpm. So I pulled the carbs off. Reset them back to 25.7 and while I had them off I figured it was a ggod time to retorque my head bolts and the new intake boots. The head bolt didn't move but the intake boots all needed about 1/8th turn each. I guess the rubber shrunk after heating. Anyway I put it all back together then colourtuned and synced again. And went for a ride. No more stumble. All gone. However after I parked it I left the fuel on reserve. The thing leaked into the air box and out onto the floor. I turned them to "on" and put some more gas into it and pulled it into the garage. Went out a couple hours later and it had flooded out again. The octy was working fine before. Do they crap out like that. It only has about 200 miles on it. Any way I I'll perform the test on it tommorrow to see if it is toast. Think I'll just get rid of it for this year and ride.
Question though. My idle seems to hang up a bit, not bad but it takes a few seconds to come back to idle. Should I resync or is this a vacumn problem.

[cywelchjr]

You don't have to get RID of it, just remember to turn off the petcocks as if you were rid of it. It will have the same affect and you won't have to replumb everything like if you take it out.

[DGXSER]

The Blame Game

Sorry to say, the octy is NOT the issue. If it is flooding, you have fuel going past the float valves. Now as much as you have been in there I hope you put new float needle valves and seats in. If not, then do so. Also, the gasket on the float bowl can edge into the float path and the floats get hung up. So, i trim the gasket to match the bowl lips on the sides. Also, wrap on the floats with the soft end of a screw driver or the like, it can shake the float loose.

Turnign the petcocks off only hides the problem it does not solve it.

[Ken Talbot]

If the octy is working and plumbed correctly, it will not flood no matter how bad the float valves are. If all the float valves are working correctly, it will not flood no matter how bad the octy is.

If it does flood, it means that the octy AND at least one float valve are bad.

[cywelchjr]

+1 on both the float valve(s) and octy being bad. You should really fix both problems, but you can until you do just turn them off, it's likely from the sound of things that it's a slow seep doing it. If that's the case it may be fine for normal riding and such but be an issue when parked. Personally, I would fix both problems, but then that's me. I wouldn't in either case though remove the octy over the issue, I'd either fix both problems or just turn them off until I got to it.

[mack]

Thats what

I was trying to get straight in my head. How could it flood if the float valves were working ok. They are new. And why all of a sudden did the octy stop doing it's job. I'll pull it apart tommorrow and have a look but I know it's plumbed properly. When I pull the carbs I leave the lines in place and just remove the vacumn hose from the octy I'll take a close look and check the hieght of the floats AGAIN, but I have to tell you that I'm getting sick of this. It worked really good when I parked it and rather than bring the stumble back I think I may opt to just turn the fuel off and ride the sh..t out him for the rest of the summer and do the sick ride thing in the fall/winter.

[cywelchjr]

The point what was well made by others is that BOTH the octy and the float valves have got to be leaking. It might even be a very slow leak. My petcocks (standard) seep a little, but it's not a problem since my needle valves don't.

Unfortunately it's hard to get rebuild kits for them that actually work, so for now I'm living with the problem. I haven't decided yet just what I'm going to do, but I may just figure out a way to make one of the kits work (apparently the nose of the valve is just enough too short to seal), I've got an idea or two, but I'm not sure if they will work, we will see.

[TopCatGr58]

Hey Mack,

THis may be late, but Reserve and PRIME come out the same front spigot, and that route BYPASSES the octy and goes directly to the carbs. So... leaving it on RESERVE was the same as PRIME, and so fuel pressure was being exerted on the carbs and the float valves, and with at least one of them being "weak", caused the leak into the airbox. Do you have INLINE FILTERS on your tubing?? Crud from the tank, the fuel lines, etc, can get inbetween the float valve and seat and keep them from sealing.

SO....your OCTY may actually NOT be leaking, but your float valve(s) did, but they also may be good and just some small pieces of crud got in there!?

Due to the probable vacuum leaks from loose intake boots, a resynch is most likely necessary, and being out of synch will cause a hanging idle.

I hope you test your OIL to make sure there's no new fuel in it! Otherwise, you'll need to change it to prevent bearing damage and ruining your engine!

T.C.

[DGXSER]

mmmmm......TC, Reserve comes out the same as ON, PRIME is its own outlet on the special petcocks. (Not often you catch The Man, gotta take advantage when it happens!!)

While it is true that both the Octy AND the float valves would have to be bad for it to leak when engine is off and petcocks both on Res or On, the point I was after is if the float valve is good, the octy can do whatever it wants or you can leave the petcock on prime and no gas will leak out the carb bowls.

[bikerphil]

Mack, you might be able to run it with the air box off to narrow down which carb is leaking. Tap the offending carb and see if the leak stops. Don't start a fire.

[mack]

got it

went out this am and turned on the fuel and watched. Still had the lower air box off. Seems it was number 1 leaking. Gave it a good rap with a screw driver. Pulled the tank and you were right. I had the lines reversed on the left hand side. Switched them around and have been watching for an hour now and have no leaks. Raining today so I'll have a beer and resync. I wonder though if the float was stuck if that didn't cause it to hang idle. Anyway, some other good news. My compression numbers came up. 140, 132, 138 &137. Good call on not pulling the jugs etc and doing a ring job.Now that it's working good I'll take it for longer rides and they may still get better. I remember the last time it was in the shop for a tune up, while the guy was strobing it, I asked what numbers he was using. I wrote them down in the book. Found it a couple days ago so I know my advance is set to 36 not 31. Going to look for a tacometer and strobe today and do it myself. Which ever of you guys said that dealers wouldn't know this bike anymore was bang on. It would seem that was the case 20 years ago as well. Thank You one and all for all the guidance, encouragement and above all sharing your knowledge and opinions with me. I couldn't have done this alone and without having you guys looking over my shoulder, I wouldn't have tried and just junked it. Many many thanx.

[thewiz]

Sounds like you have ..

it whipped. I didn't say that anyone else posted this but if they did, please excuse the duplication.

Check you oil level before you run the motor extensively. Beside what gas you see on the floor, many times the gas will leak down into the crankcase and fill it with gas as well. Not good.

[Bullet]

140 comp is nothing to sneeze at ..

keep the seafoam in the oil, the comp should get a bit better as you put some miles on it ..

I spent a ton of hours on my carbs before they went on the engine.

checked, double checked and.. I still had 2 leakers at first, so I trimmed the bowl gasket flush on the inside to the bottom of the carb body on all 4 carbs .. no more leaks .. matter of fact, I don't even turn my petcocks off now, and I ditched the octy when the engine went in the bike ..

the float can get hung on these old mikuni's ..

almost 30 years of wrenching boats, bikes and atv's, I have never seen any carb's as bitchy as these old mikuni's ..

enjoy !!

[natemoen]

Sounds like your well on your way! Great work!

[fredintoon]

Ditch the octo!

- - - Pulled the tank and you were right. I had the lines reversed on the left hand side. Switched them around and have been watching for an hour now and have no leaks. - - -

Hi Mack,
from reading your posts it seems to me that you are Mr. Meticulous.
That someone as careful as yourself could mis-plumb the octo tends to demonstrate that a system that uses 8 fuel hoses, 4 gas spigots, a vacuum line and an extra widget just to turn the gas on is perhaps a tad too complicated for it's job.
Back in the days of the P38, Lockheed's Chief Designer had a big wall sign that said:-
Simplificate and add lightness
For the average shade tree mechanic, replacing the octo with two fuel lines and capping the PRIME spigots and vacuum tap would go right along with that wall sign.
Just remember to turn the gas off when you stop, like grandpa used to do.