Troubleshooting motorcycle...

[Ophidia]

Hey
Some of you may remember my post in the not too distant past about getting my late father-in-law's old '79 Honda CB750K running. I have some more problems, and was wondering if anyone could give help.
Original post here:
http://archive.reefcentral.com/vbulletin/showthread.php?threadid=22042

Well, stating the problem is actually rather simple: the bike has no power. I have changed the oil and gas, changed the spark plugs, and run it abot 20 miles now. It starts fine, seems to run smoothly, but has very little power when riding it. The air cleaner is clean, and the engine does not hesitate when I crack the throttle (after it warms up) but it does not seem to have any get-up-and-go.

Is there any gas additive that might be safe to put in it to remove any residual crud that may be in the carburators? Or is this bike simply supposed to be a gutless pig. It would seem to me that a 750 should have prtty good get-up-and-go-- the 700 Yamaha we have is really ballsy-- but there is not much there.

Any thoughts?

Thanks
Chris

[mr. pluto]

could be clogged main jets, improper needle jet position,
or bad coils..just to start.. what color is the carbon
on the pipe?

[Clyde]

also check your sparkplugs, on bottom what color are they ?

brown, white, or oily ?

those are great tattletales for adjusting your carb

[puff the magic fish]

You could also check the compression in the cylinders, it may just be old and worn out.

Have the carbs professionally cleaned and tuned, it is pretty hard to get the mixture right by "ear".

puff

[Ophidia]

Thanks for the replies, all.

The bike is in Fergus Falls, MN, about 300 miles away, so I can't check it out right now, but I will answer the best I can.

Mosey, I am not sure what color the carbon on the exhaust was. I vaguely remember black, but not sure...

Clyde,
The threads on the old plugs were oily, and the bottoms were black. I replaced them with new NGK plugs.

Puff, when I get it down here to Rochester, I will have to bring it in to have the carbs clenaed and adjusted (I would only make it worse trying to do it myself). I was just hoping htere would be a quick, easy fix. I would assume that a compression check would be cheap, so I will have that done as well.
The cam chain is very noisy as well. Hopefully it can be tightened.

Does the black spark plug thing sound like a carb adjustment problem? It sounds and smells like it is running rich.

Any more troubleshooting tips?
Thanks!
Chris

[Clyde]

okay if plugs oily etc, like you said could be running rich..

rich wont HURT the motor, too lean will pop a hole in the piston :)

anyway, see if sparkplugs will make it nice and new - and last for a short time before it gets all fouled up, then your carbs might be set at too rich settings.

now, compression rather cheap really - its just a pressure gauage that you screw in your sparkplug holes, and pump the kicker for a few times, then you record the compression in it.

someone charge you 30 bucks for it ? forget it buy your own.

I paid like 45 for mine, mine has a long long tube, I use it for snowmobiles, I have 3 pistons on mine, I chekced mine like a few months ago during the snowmobile season, still kicking good.. I think my buddy has it now, I have to go over and get it from him...