Topic: Runaway Revs, Low mpg, air pods....connected issues?

[John Eberly]

If you release the clutch a little but don't ride away, then pull the clutch back, does it rev back up or does it idle down? If it does not rev back up right away your advance springs are suspect.

[hman0217]

In fact, it will idle high at a light and then when I release the clutch, it will drop to normal. Not exactly what you said but I think it confirms the same thing, no?

Not exactly. Engaging the clutch puts load onto the engine, so it will naturally reduce the RPMs. However, once in gear and riding, does the idle race up again? OR does that moment of loading the engine restore the idle temporarily?

The high idle has been typically happening with the clutch engaged. However, I have noticed that a couple of times recently, I would be moving along in low gear and the revs would not be sky high, as in neutral, but would be a bit beyond expected for the given throttle (I checked throttle return line and it seems fine). Once I'm trucking though, everything behaves wonderfully.

I started getting into the rest because I started to discover disappointing evidence that the fellow who I have my bike to last did a shoddy job and I don't want to assume anything was done correctly (he even told me that he put in 115 jets and I found 120 jets in there, for just one example) now I'm adamant about being my own mechanic.

So with thoughts that poorly synced carbs could be an issue AND that airpods make everything wacky unless major other alterations are made, I started chasing down these matters.

Having said that, in the interest of thoroughness, I do now wanna pull these out and check them too, unless you all think the symptoms would rule it out.

Thanks

[hman0217]

If you release the clutch a little but don't ride away, then pull the clutch back, does it rev back up or does it idle down? If it does not rev back up right away your advance springs are suspect.

Typically revs back up

[John Eberly]

That makes it less likely that the advance springs are the problem

I'd keep it in mind though. The Honda system is really more a spark retard system to make starting and idling easier. The centrifugal advance comes in pretty early and pretty much all at once. It really makes the engine come alive, and if the springs are weak or the advance is stuck wide open you will have a devil of a time getting the bike to idle. Maybe have a look, make sure the plate rotates easily, and see if you can find anything wrong.

[hman0217]

That makes it less likely that the advance springs are the problem

I'd keep it in mind though. The Honda system is really more a spark retard system to make starting and idling easier. The centrifugal advance comes in pretty early and pretty much all at once. It really makes the engine come alive, and if the springs are weak or the advance is stuck wide open you will have a devil of a time getting the bike to idle. Maybe have a look, make sure the plate rotates easily, and see if you can find anything wrong.

Yea I really hope it is because that's more easily rectifiable than an internal vacuum leak....by far. Can't get to it again for a few days but I'm figuring I'm gonna go ahead and replace them anyway just incase, to check that off the list... does anyone have a good source for the ignition advancers? Or at least the springs for them?

I can only find used ones on eBay and I'd rather have a new one than one that's coming off a 40-year old bike. Google search isn't turning up much.

Thanks again

[flybox1]

Yamiya sells the springs....but I really doubt this is it.

Verify if the following has been done.  Pictures are proof.

Fuel height set to 3-4mm below bowl gasket seam. Picture of the fuel in the clear tubes.
Vacuum sync of all carbs.  Picture of the gauges.
Idle plug chop with new plugs.  Picture of all the idle chopped plug insulators.

[hman0217]

Yamiya sells the springs....but I really doubt this is it.

Verify if the following has been done.  Pictures are proof.

Fuel height set to 3-4mm below bowl gasket seam. Picture of the fuel in the clear tubes.
Vacuum sync of all carbs.  Picture of the gauges.
Idle plug chop with new plugs.  Picture of all the idle chopped plug insulators.

Roger that. My attempted carb synch Sunday was a disaster...needles just went crazy in the red major-vacuum-leak-or-ignition-advance-issue zone. Granted, I didn't have my clear tubes yet and hadn't done the clear tube method. I now received them. This coming Sunday I will attempt all the above and supply pics thoroughly.

One thing though, when I unscrewed the number 3 vacuum screw, I found the washer was gone - that really paper thin washer that goes between the screw head and the carbs. 1, 2 and 4 have the washer. How critical is this piece? Is this affecting me from getting a good seal?

[flybox1]

Hard to say, but these really are not needed....as long as the screw is seated, it will seal.
My F engine does not have these.

What type of vac gauge do you have.  Liquid or dial?  If dial, did you calibrate them?
How do you know your vacuum was too high? 
Its all relative.  The vacuum levels only need to read the same.  The actual # is somewhat irrelevant.
If there was such a variance between them, its clear to me another attempt at a bench sync is needed....first. 

[PeWe]

Advancer springs can be fixed with a cutter an flat plier. I cut both mine 1/2 wound and reshape that en to fit the pin the spring is attached to.
Possible to do only 1 to start with.
But check ignition first. If you set F correctly at idle and full advance kick in at around 3000rpm for CB50x Ok, right?
My CB750 full advance around 2600-2700 after the fix. Before full advance at 1500-1800rpm

[hman0217]

Hard to say, but these really are not needed....as long as the screw is seated, it will seal.
My F engine does not have these.

What type of vac gauge do you have.  Liquid or dial?  If dial, did you calibrate them?
How do you know your vacuum was too high? 
Its all relative.  The vacuum levels only need to read the same.  The actual # is somewhat irrelevant.
If there was such a variance between them, its clear to me another attempt at a bench sync is needed....first. 

It was dial.

http://www.ebay.com/itm/391545962276?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The needles weren't even holding still. they were fluctuating like crazy, easily about a 45 degree oscillation around the circumference. But yes, let me do a proper calibration and see whether that makes a difference.

[flybox1]

I have similar dial gauges.
You need to use the in-line adjusters to quite the bounce. Install one on each vacuum line up near the dials.
Each gauge should be attached, one at a time, to one of your carb vac sync inlets.  They can all be adjusted to read the same vacuum by turning that brass screw on the lower dial face.
Then, you're good to go with syncing all four carbs together.

[hman0217]

I have similar dial gauges.
You need to use the in-line adjusters to quite the bounce. Install one on each vacuum line up near the dials.
Each gauge should be attached, one at a time, to one of your carb vac sync inlets.  They can all be adjusted to read the same vacuum by turning that brass screw on the lower dial face.
Then, you're good to go with syncing all four carbs together.

And by brass screw, I take it you mean these plastic screws pictured below in my case.

[flybox1]

NO....those white things are damper valves.  you need to install them IN LINE...one each gauge tube.
See my shiity drawing 
 
The gauge calibration screws are ON THE DIALS...under the clear plastic dial face cover.  see picture

[lrutt]

12mpg, there would be friggin raw gas coming out the exhaust FSS.

I have to say though, and no offense, but if you think that the tach cable seal could be a source for your vac leak, I think you need to get someone who really knows motors to work with you. These systems, carb, electrical, and cam/valves/pistons (mechanical) all have to be in top shape and in sync for an engine to work properly. Any one out of whack and it's like a 3 legged stool,,,,picture that.

So eliminate things one at a time per a lot of the recommendation above.

Where are you located, there might be a member close by that can give you pointers. if you are close to Orlando I'll help out.

[hman0217]

12mpg, there would be friggin raw gas coming out the exhaust FSS.

I have to say though, and no offense, but if you think that the tach cable seal could be a source for your vac leak, I think you need to get someone who really knows motors to work with you. These systems, carb, electrical, and cam/valves/pistons (mechanical) all have to be in top shape and in sync for an engine to work properly. Any one out of whack and it's like a 3 legged stool,,,,picture that.

So eliminate things one at a time per a lot of the recommendation above.

Where are you located, there might be a member close by that can give you pointers. if you are close to Orlando I'll help out.

No offense taken. I'm not claiming to be an expert and I've learned a good deal about the bike, though I realize I've got a lot more to go. And I have to give a lot of thanks to the patient folks on the forum for all your patient advices.

I also got taken for a ride last time I handed someone my bike so I guess I'm having trust issues.

Having said that, I live in Brooklyn, New York and would be willing to travel up to a hundred miles or so, on my 12 mpg bike, if anybody DID want to give a hand.

Barring that, unless I'm causing serious psychological harm to anyone, I'd like to continue to take advantage of the kindness of all you more knowledgeable folks.

I'll be trying all the above and reporting back, in pictures, on my progress on my next day off. Thank you, Lrutt, for offering to help me out.

[evinrude7]

this is a great thread for me.  i'm sort of in the same boat with my 750.  i'll follow along for now.  big change after i lost the pods.  i think hman did the same. 

[NobleHops]

Don't be put off, you're doing great, just take and follow the good advice you are getting and be methodical. And this IS good referenceable content for others, as was offered.

[hman0217]

Don't be put off, you're doing great, just take and follow the good advice you are getting and be methodical. And this IS good referenceable content for others, as was offered.

Thanks. I do feel like a clown with my silly questions but, again, everyone with the knowledge and the know-how is working on their own bikes and so I'm stuck figuring this out...

So I ordered the wrong size clear tubes (1/8") and so Sunday I was dead in the water until the 3/16" come in hopefully tomorrow. I even tried boiling the 1/8"s and it didn't work (I'm using the carb synch tool brass extensions to insert the tubes into the plugs at the bottoms of the carbs.

Anyway, I figured I'd do my valve tappet clearance too, because although i've only put 2500 miles on the bike the past year, it's been 12 months since I did it and wanted to make sure that wasn't causing an issue.

And the darn valve covers are stuck like glue. I've already come dangerously close to stripping the #1 and #4 inlets and then I stopped. Tried a 17 mm open wrench, closed wrench, crescent wrench, vice grip with a hammer and the 17 mm socket wrench. Nothing...

Question: If I warmed up the engine, would that make them looser, tighter or make no difference? IF that's not the ticket, then how do I get these suckers off?

Also ordered new springs for the ignition advancer to change out anyway and rule out that potential just in case. But yes, I'm still planning on going through the sequence outlined above methodically.

[flybox1]

Don't be put off, you're doing great, just take and follow the good advice you are getting and be methodical. And this IS good referenceable content for others, as was offered.

Thanks. I do feel like a clown with my silly questions but, again, everyone with the knowledge and the know-how is working on their own bikes and so I'm stuck figuring this out...

So I ordered the wrong size clear tubes (1/8") and so Sunday I was dead in the water until the 3/16" come in hopefully tomorrow. I even tried boiling the 1/8"s and it didn't work (I'm using the carb synch tool brass extensions to insert the tubes into the plugs at the bottoms of the carbs.

Anyway, I figured I'd do my valve tappet clearance too, because although i've only put 2500 miles on the bike the past year, it's been 12 months since I did it and wanted to make sure that wasn't causing an issue. Cool.  If they are out, its good practice.  If they pass go/no-go, pat yourself on the back for getting it right last time.

And the darn valve covers are stuck like glue. I've already come dangerously close to stripping the #1 and #4 inlets and then I stopped. Tried a 17 mm open wrench, closed wrench, crescent wrench, vice grip with a hammer and the 17 mm socket wrench. Nothing...
New orings are really good here.  They allow you to lightly set them, which is all thats needed to seal.  If the orings are dry and shrunken, yes, you have to overtighten them to get a seal. They dont live under oil here, anyway.  No need to crank them down.

Question: If I warmed up the engine, would that make them looser, tighter or make no difference? IF that's not the ticket, then how do I get these suckers off?  Once these are stuck to the valve cover, it is not uncommon to have one shear off.  Heat/PB blaster cycles can help.

Also ordered new springs for the ignition advancer to change out anyway and rule out that potential just in case. But yes, I'm still planning on going through the sequence outlined above methodically.

[hman0217]

Once these are stuck to the valve cover, it is not uncommon to have one shear off.  Heat/PB blaster cycles can help.

can I use a Propane torch applied directly to the covers for the heat option?

[flybox1]

sure.

[NobleHops]

I get them in for vapor blasting and sometimes they feel nearly welded to the covers too. In this case I have the advantage of them being on the bench. I will sometimes lay a square of aluminum foil over the cover, or sometimes even two, and then press a box wrench over the foil onto the tappet cover. That seems to tighten up the fit of the wrench enough to get them free without further damage.

I also use my electric impact with a 6-point socket and the foil trick, but again, that's on the bench where there is no issue with access.

[evinrude7]

Once these are stuck to the valve cover, it is not uncommon to have one shear off.  Heat/PB blaster cycles can help.

can I use a Propane torch applied directly to the covers for the heat option?

hman, i had the same issue with the tappet covers.  use the closed end wrench on the nut part and a vise grip on the outer part at the largest diameter of the cover simultaneously.  run the bike a few minutes then have a go at getting them off.  when you put them back on don't wrench them real hard. 

[hman0217]

Alright...the bike is running like a top now. There was no major air leak or vacuum leak and there was no issue with the ignition advancer springs. The guts of the carbs were also fine. It was exactly as you folks said - starting from the very beginning and going through all items one by one. The following were found:

1. valve clearances were off
2. the air screws, at one turn out, were providing way too little air to the mixture
3. the carb synch was way off, though fixing issues 1 and 2 probably shifted the carb synch anyway

Truth be told, I did enlist the help of a local honda stalwart to help me go through this and I'm glad I did. At one point, I had to decide that I wanted to .... well .... ride my bike!

But for the interest of completing this thread, I wanted to update you all on our findings.

I still haven't filled my tank yet so I don't know how much better my fuel economy is. But once I get  a warm idle it stays right where it is.

Thanks again, everyone, for all the pointers you gave. I still need to learn this all myself if I'm to have this bike for a long time. So this has been a learning experience.

[flybox1]

Nice work.