Topic: Swapping out spark advancers

[AbbyRider]

Are spark advancers specific to engine models? My '77 CB750F advancer had one of the little nubby things sheared off, so I looked at the one from my K1 engine and the markings were exactly the same distance. So I swapped it on. I've set the timing, and while I did almost run out of slot room on the points plate, it is idling fine etc. The engine is running EXTREMELY hot though. I originally thought it was just running really lean, so I've been adjusting for the lean condition. Plugs are starting to look a bit better. But the engine is running so hot that I haven't done more than drive around the block when testing carb and jet settings.

After searching here on the forum, I found that bad spark advance leads to running really hot, and I'm wondering if the K1 advancer could be the issue? I'd be forced to either weld on a new little nubby, or try and find a replacement advancer. But don't want to do so if I'm barking up the wrong tree.

[Tews19]

My K1 advancer need to be cleaned and relubed. I put on a 323 marked one from my 550F. It runs just fine so I left it.

[MCRider]

There are tiny differences per part number. But since they are all 750s you'll just change the character of the ride a tiny bit.

The "323" is a 500/550. I've heard over the years of 750s running a 323 and liking the feel better. Then again it will depend on which 750.

The cam timing did change over the years and if you mix and match the advancers you'll get a different result.  But I've never hear of a problem.

If it were me I'd put any advancer in it I coud find and see what I thought.  I have several I think, but I want (need) money for them/it.

[70CB750]

I believe the later models are made run leaner (due to the oil shortage of the time period) partially by the design of the advancer.  I remember picture of 3 advancers documenting that, must have been Hondaman's book.

[AbbyRider]

Ok. So sounds to me like there may be minor differences, but nothing that would cause a huge issue with the engine overheating. I could actually run it with the original advancer - only issue with not having the little nub is that I wouldn't be able to rotate crank using the bolt on that end.

[dave500]

have a look how much free play or slack you might have when you fit it up,most have a couple of degrees,unless you index it properly the actual numbers will be hit or miss to some extent,heres one with the piston dialled to the tdc mark,and heres the amount of travel left or right it has between the crank hole and the locating pin,some will be more or less,so where will it be when you tighten the bolt?

[MiGhost]

One of the biggest differences in the advancers will be the springs, and flyweights. Not readily visible differences, but will change the timing advance characteristics a bit. Nothing that will kill the engine though. Hondaman has documented some of the differences.

[Nic]

have a look how much free play or slack you might have when you fit it up,most have a couple of degrees,unless you index it properly the actual numbers will be hit or miss to some extent,heres one with the piston dialled to the tdc mark,and heres the amount of travel left or right it has between the crank hole and the locating pin,some will be more or less,so where will it be when you tighten the bolt?

My 750 K2 had a lot more play that that, I drilled out the hole in the crank and made a brass bush, now it's solid, no play at all. Peace of mind.

[AbbyRider]

Interesting. I grabbed both of them and they had about the same amount of free play. The stock '77 is a TEC 300; the one off the K1 has a logo of what looks like crosshairs over a squared off "O". I think I'm gonna put the stock one back on there, but weld a little nub back on. Also going to order up some fresh points and condensers and do the whole proper tune once again so that I can eliminate any questions.

[MCRider]

Interesting. I grabbed both of them and they had about the same amount of free play. The stock '77 is a TEC 300; the one off the K1 has a logo of what looks like crosshairs over a squared off "O". I think I'm gonna put the stock one back on there, but weld a little nub back on. Also going to order up some fresh points and condensers and do the whole proper tune once again so that I can eliminate any questions.

When finishing mine, I tried the advancers I had and went with the one with the least pin/hole play. I would like to get one with as little play as possible, but fact is, if its done right, the big nut should hold it in place so the play is never really a factor. IT could be that one sets the advancer to full adv or ret, pin it down with the nut and see which way runs best.

I was going to use an old Prestolite ignition, but it wouldn't time up (I have the instructions if any one needs them). So in shopping for an ignition I settled on a TEC point plate with a HondaMan transistor pak. Very happy.

[Nic]

Interesting. I grabbed both of them and they had about the same amount of free play. The stock '77 is a TEC 300; the one off the K1 has a logo of what looks like crosshairs over a squared off "O". I think I'm gonna put the stock one back on there, but weld a little nub back on. Also going to order up some fresh points and condensers and do the whole proper tune once again so that I can eliminate any questions.

When finishing mine, I tried the advancers I had and went with the one with the least pin/hole play. I would like to get one with as little play as possible, but fact is, if its done right, the big nut should hold it in place so the play is never really a factor. IT could be that one sets the advancer to full adv or ret, pin it down with the nut and see which way runs best.

I was going to use an old Prestolite ignition, but it wouldn't time up (I have the instructions if any one needs them). So in shopping for an ignition I settled on a TEC point plate with a HondaMan transistor pak. Very happy.

It's actually the hole in the crank that wears and gives most of the play, and it's the smaller 10mm nut (6mm thread) that holds the unit in place. I have H/Man's tranny ignition as well with the tec plate etc n like it.

[MCRider]

Interesting. I grabbed both of them and they had about the same amount of free play. The stock '77 is a TEC 300; the one off the K1 has a logo of what looks like crosshairs over a squared off "O". I think I'm gonna put the stock one back on there, but weld a little nub back on. Also going to order up some fresh points and condensers and do the whole proper tune once again so that I can eliminate any questions.

When finishing mine, I tried the advancers I had and went with the one with the least pin/hole play. I would like to get one with as little play as possible, but fact is, if its done right, the big nut should hold it in place so the play is never really a factor. IT could be that one sets the advancer to full adv or ret, pin it down with the nut and see which way runs best.

I was going to use an old Prestolite ignition, but it wouldn't time up (I have the instructions if any one needs them). So in shopping for an ignition I settled on a TEC point plate with a HondaMan transistor pak. Very happy.

It's actually the hole in the crank that gives most of the play, and it's the smaller 10mm nut (6mm thread) that holds the unit in place. I have H/Man's tranny ignition as well with the tec plate etc n like it.

U R keerect, my brain fart.

[754]

I am thinking , that with the cam timing changes with late cams, the earlier. Advance may not be ideal. I should. Have A few  different advances what number was on yours?

[AbbyRider]

Thanks Frank. Mine is a 300. But I did manage to weld and shape a decent nub back on, so I think I'll just try this one. But if I experience some issues I will definitely take you up on the offer.

[Don R]

 How does one know when his bike is running too hot. It seems to be a very subjective deal unless you use an  infrared thermometer or something.

[lrutt]

I might add that lubing the advancer is a critical part of maintenance. Easy to do and will help them last a life time if done regularly.

[AbbyRider]

How does one know when his bike is running too hot. It seems to be a very subjective deal unless you use an  infrared thermometer or something.

Usually when it's borderline, it's subjective. In my case, one trip around the block gets the engine so hot that not only can you not touch the valve cover - you can't even get your hand near it. It's too hot to touch all the way back to the trans cover. Even the oil seems like it's losing viscosity. I know it shouldn't get like that from a 2 minute jaunt.