Topic: ENGINE TEMP CB500 - too hot? Just jetted richer...

[zanorak]

Hello all. Thanks for your input thus far - the forum is great for all my questions already asked and answered. Here's one that didn't come up on the search....

1972 CB500
Carbs cleaned and re-jetted (N424-24) to #42 Pilot, Main jet #115.
Pod filters, 4 to 1 exhaust.

Previously was underjetted like crazy on the pilot (someone put a mikuni or other jet in that was only 20mm long - didn't even draw fuel half the time) and stock on the main. (#100)

I took them apart, cleaned them rigorously, reassembled with the new jets. (carbs look to have been rebuilt before, seals etc were newish)

Fuel system has been cleaned, running filters, and flows well.

So here's the thing - with the rich jetting in the carbs it now seems to run HOTTER than before! Can anyone explain this to me? I know it was 80 degrees today but it's too hot to touch after 40 minutes of riding. I have the air bleeds at 1/2 turn. (turned out until it started to sputter then back in 1/4 roughly)

This is pretty confusing to me and I don't want to damage the engine. Any thoughts? IS it supposed to be this hot? How hot can it be and not fry?

As above, thanks for all your responses ahead of time!

[svenD]

how much experiance is on hand with aircooled mc motors,
youre not supposed to be able to touch it when hot(unless your very unsensitive)
these motors keep their cool by radiating heat.
if in doubt about your mixture do a plug chop.
a malajusted ignition can cause overheating.

[Scott S]

 Yeah, I wouldn't even THINK about touching any of my motorcycle engines after 40 mins of riding!
 Have you checked the timing? Timing can have a big effect on air cooled motors.

[Bodi]

It can get very hot. The finned part can get very hot indeed: not the flesh sticking burn hot of the exhaust headers but hot enough to give you a blistering burn in a second or two.
The basic fact of heat transfer is that energy moves from hot to cold at a rate proportional to the temperature differential.
Actual damage from overheating is pretty rare, as the engine gets hotter it gets more efficient at dumping heat... heat produced and heat dumped normally balances out somewhere before meltdown is reached.

[dave500]

if your not leaning out when you open the throttle a little fast,,not like real fast or it will lean out,ide say its ok,these are a hot engine,i only commented the other to my neighbour who has just bought a new suzi vstrom (water cooled)you could sort of touch his motor after a ride but then touch mine and its easily hotter!you cant hold your fingers on say the alternator,the head will be hotter.

[zanorak]

Thanks for the replies!
Yes, I think this is normal operating temp. Previously the bike wasn't running well and I think that made it too cold blooded - gave me no real idea of what to expect. All of your posts have confirmed this for me. SOHC4 rules! I tore ass all over today on this bike and it was probably one of the best Saturdays I've had in months.

[dave500]

yeah if its not real #$%*y when cold itll be ok.when its hot, and been ridden for a while ,in neutral,dont let the revs get under about 2500,then twist open real fast over and over to say 5 or 6 grand,no flat spot?or just a little,thats ok,no black clouds of unburnt fuel?shell be right,,we dont have ethanol in our 98 octane here,,man we got it good.

[zanorak]

Naw, she loves everything over 3000 rpm. A little stumble between 1500 and 2000. The new jets make the exhaust a little thick but not too much more than before. Actually, when she revs off idle now the smoke is a little brown like a turbo ricer's exhaust. I think the jetting is right on. Later I might drop my needles back down to the first notch from the top but right now I think it's sorted. I haven't taken the bike over 50 thus far because I'm having trouble with the front wheel now - it appears to wobble then bounce and both tires are losing air pretty quickly. Funny how these old machines nickle and dime you huh?

[dave500]

err,get those tires and balance sorted before you think of going faster!ill talk to you then.i dont blow any smoke.and youll soon find nickle and dimes add up to real dollars.

[zanorak]

Thank god i only paid 200 bucks for this thing! I've already spent twice that I think...

I think I'm going to have to get the front wheel trued up. WHich means that while I'm at it I'm going to have to replace the tire since it's a little >cracked< and dryrotted. THere's another 150 bucks I think.

[spot45]

What!?  You are riding with old, cracked, dry rotted tires?  There is your wobble problem right there.  Put on some new tires on it and get the wheels balanced.  If you keep riding it the way it is now you will get yourself killed.