96 CB500 - T

Hello, I wonder if anyone has come across anything similar?




I am coaxing a 96
500-T model back to life. It was
given a full service by a Honda dealer three years ago and the last owner has
not started it for about 2 1/2 years. So
far I have:


·
Replaced the battery


·
Spark plugs


·
Oil and filter.


·
Drained and replaced the fuel in the carb bowls
twice.





I have tried starting the bike twice on the centre stand, I
am waiting for a helmet and am uncertain whether to try a road test. On both occasions:





·
The bike started straight away but miss firing badly
(suspect left cylinder as down pipe takes longer to heat up) and running
evenly.


·
Once warmer after 4 minutes the miss fire is
greatly reduced at tick over and when revving the engine.


·
The temperature gauge rises and on both
occasions nearly got to the ‘red zone’ before I turned the ignition off. It took about twenty minutes for this to
happen. I was expecting the electric fan
to cut in but it did not.





I was hoping to avoid a full strip down of the carburettors
and I have avoided using cleaning spray as this is supposed to make rubber
gaskets etc swell. I am wondering if I
have two faults here, or is the constant temp rise is due to misfiring, and
will a road test cool the radiator sufficiently and possibly clean out what
could be sticky carb jets?





The engine is remarkable quiet and appears to be fine once
over the initial start and before I become concerned about the temperature.





Thanks for reading and any comments welcome.

Welcome in mate!
I would swap the coils for starters to see if one is at fault.
A common fault with the rad fan is for the earth lead to snap off; it originally attaches on the top rad fan bolt, you can either crimp on another connector or bare the lead back and wrap it round the bolt before tightening.

Thanks.

If it's misfiring from cold, then it won't have anything to do with the cooling system until the engine gets up to temp.
A lot of older bikes with carbs run like dogs until warmed up slightly - does it misfire wiith the choke on? If it doesn't, then it's just a cold engine.
Don't forget it's an old ish Honda parallel twin, so they are never going to run as smoothly as a modern FI bike.
Have you balanced the carbs? Very easy to do if you have access to a vacuum gauge and screwdriver, or find somebody who does.
Also, drain the fuel and take off the carbs. Remove the idle and main jets, and blast them through with carb cleaner or similar (don't shove metal wire through them). Could be that they got clogged up when the bike stood for a while, causing rough running. Not as tricky as it sounds, just that everything in this bike is packed in pretty tight and can be tough to remove. You don't need to 'fully strip' the carbs, just drain them and flip them over, remove three screws and you're in there. You don't need to adjust any settings. Buy a Haynes manual or download a free one.
As for the fan I haven't really poked around with mine - are you able to run 12v across the terminals to make it work? Or the thermostat may be shot. Again, have a look at the manual.

The rising temperature *should* trigger the fan to switch on - if not, there are two causes (as identified above) 1. a knackered fan motor or 2. no earthing on the radiator.

1. can be tested by disconnecting the fan from the bike electrics and connecting it to the battery

and

2. can be fixed by running some wire from the radiator body to (almost) anywhere else on the bike. You can use one of the radiator side-screws to attach the random wire....


Anyway, the fan problem won't stop you from taking it for a spin, assuming there is coolant in there (you should check this). The engine won't overheat as you are moving which forces cool air through the radiator.

Once you have taken it for a ride you will/might be able to assess how well (or otherwise) it works - this will tell you wether your problems are limited to rough-starting or something more serious.

Good Luck!

Thanks

Problem with radiator fan solved, no earth conncection. Took carbs off cleaned both primary and main jets (already very clean). Have good strong spark both cylinders both appear to be getting fuel. However left hand cyclinder still only occasionnally fires around 200RPM.

Will post another post with this us, thanks for your time.

Rob