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NUTS. '78 750 is smoking out the left pipe.

  • Thread starter Thread starter Fast Doc
  • Start date Start date
F

Fast Doc

Guest
This is my spare bike. It is properly stored 11 months out of the year and comes out once a summer for a vacation ride when my friend from NJ comes out to visit. It has 39,000 miles on it and it is well maintained.

It used a little oil, maybe 1/2 quart per 2,000 miles, and does not leak. It would smoke a little when first started in the summer, but nothing remarkable. Sometimes after spending some time on the sidestand it would smoke a little for a minute or so.

I had it in the shop to get the carbs synched; I don't have a manometer anymore. The shop could not get to it for about a month, while the bike sat on it's sidestand. When he started it up today, he said the left pipe smoked a lot, filled his shop with smoke in fact. Then the smoking stopped.

He said the left outside plug was oil fouled, and he replaced it. He also said the gap was very narrow, for some reason. He replaced the plug and now it runs fine.

I plan to take this bike to Yellowstone in a few weeks, about 2,000 miles roundtrip. Am I OK?

To me it sounds like a leaky valve guide seal, and being on the sidestand caused the oil to leak into the cylinder.

Do I have a problem here? What should I do?

Bill
 
i think you're right on the valve seals being the prob
so, just ride it and check the oil level reagularly
 
Just use the side stand, Should be no problem just keep an eye on the oil level. Might take an extra sparkplug with you
 
How long will these bikes go with bad seals? Like I say, it only gets used about 2,000 miles/year, usually in about 7-9 days. The rest of the time I ride my other bike. I just don't want to break down on the side of the road in Wyoming somewhere, although I can think of worse things!

Now she sports a Vetter top case and saddlebags. She's a nice old bike.

DSC02001.jpg
 
Fast Doc said:
How long will these bikes go with bad seals? Like I say, it only gets used about 2,000 miles/year, usually in about 7-9 days. The rest of the time I ride my other bike. I just don't want to break down on the side of the road in Wyoming somewhere, although I can think of worse things!

Now she sports a Vetter top case and saddlebags. She's a nice old bike.

DSC02001.jpg
Click to expand...

I know it's a pain to be left stranded on the roadside.

BUT WHAT A VIEW!!!;)
 
an optimistic view

an optimistic view

the bike can run without the seals
may smoke a bit more though :rolleyes:

and even if the seal disintegrates completely, all the pieces should still stay in the valve bucket :D
 
A bad valve seal will not cause a breakdown as long as you keep oil in it.
 
Thanks for the information!

I took the bike to work this morning and she was fine, I left her on the sidestand overnight and no smoke.

BUT,

Now there is a 'miss' on acceleration from low RPM's that was not there before. Cruise and idle are fine, but there is this little miss when on the gas from lower RPM's. I don't know if it's ignition or carburation, but I'm thinking carbs.

Vacuum leak?

Other work that was done at the shop includes a tune up (plugs, points, condensers), carb synchronization, and clutch replacement.
 
Fast Doc said:
Thanks for the information!


Other work that was done at the shop includes a tune up (plugs, points, condensers), carb synchronization, and clutch replacement.
Click to expand...

OK...so that wasn't a cheap month at the shop! :eek:

Could be a little crud in a carb passage, somewhere. If it were me and it only does it when moderate throttle roll and under heavy load, I'de treat it to a good dose of Seafoam or two, and ride it.
 
Start easy. Check the plugs for fouling. If the guy smoked out the garage this could foul a plug easily.
 
Plugs are fresh since the smoking incident.

Could the new points have done this if they are not adjusted right? It does not feel like a miss; there is no backfire or spitting, more of a stumble.

IIRC there is an easy way to check for air leaks by spraying carb cleaner on the intake boots while the engine is idiling and seing if the RPM's rise, or something like that?

I'm game for some Seafoam or Marvel or Gumout or somehting and giving it a try. The funny thing is it did not have this problem before it was serviced.:confused:

And yes, it WAS a pricey trip to the shop. I could have done it by myself, but I've been busy at work and time is money also. I figure I make more in an hour than the mechanic does, so it pays for me to do what I do and pay him.

That's my logic, anyway!:)
 
Use WD40 or the like-carb cleaner is pretty flammable.
Not that WD isn't, it's less flammable than carb cleaner.
 
Exactly what do I do and what do I look for? Was I right in my previous post?
 
Fast Doc said:
Plugs are fresh since the smoking incident.

Could the new points have done this if they are not adjusted right? It does not feel like a miss; there is no backfire or spitting, more of a stumble.

IIRC there is an easy way to check for air leaks by spraying carb cleaner on the intake boots while the engine is idiling and seing if the RPM's rise, or something like that?

I'm game for some Seafoam or Marvel or Gumout or somehting and giving it a try. The funny thing is it did not have this problem before it was serviced.:confused:

And yes, it WAS a pricey trip to the shop. I could have done it by myself, but I've been busy at work and time is money also. I figure I make more in an hour than the mechanic does, so it pays for me to do what I do and pay him.

That's my logic, anyway!:)
Click to expand...

Double check your oil level. I had a leaky petcock and fuel leaked into the crankcase and caused it to me too full. Left side would smoke after setting on side stand, 1 & 4 plugs would tend to foul and miss as the cylendars are lower and would get fuel dilluted oil forced up past the rings. If it is oil seals add a little synthetic oil when you top off the oil level next time. Synthetics can soften hard seals and make them swell a bit.
 
Update:

A can of carb cleaner in the tank cleared up the stumble. Part of the 'problem' is I am used to a fuel injected 1800cc Gold Wing and I'm not yet natural with these old non CV carbs and they have peculiar low RPM/high manifold pressure charateristics.

No leaks.

Now the left fork leg is off getting a new seal fitted :( ... It's always soemthing with old bikes!
 
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