Scooterotica

Can anyone shed any light on cylinder head temperatures, whats a good range to run at?
Running a Rapido 240ish built by JB, 30mm delly & JL3, when ridden hard on the motorway it runs between 320-350 f. Cruisin runs between 305-320. Is this an expected range?
Also run a GT206, 30mm & JL3, that runs hard at 180-200 C,a lot hotter than above, and cruises at 160-180, again seems hot compared to the other. I know it would have been better to measure them in the same temp but was curious.
If running hot what effects this, lean or rich etc., The Rapido was set up on a dyno so should be a good benchmark, but most advice on temps seems to lean toward EGT.

I run an a Taffspeed RB 250, with 34 Delly and an Franspeed pipe, full frame bike. I have a micron 4 tacho with TC off the spark plug, under 7000 rpm it runs at about 180*C above that it gets up to about 220*C. I've never really had it flat out for long periods but if I let it labour up hills the temp does go up a bit quick. I used to think over 200 was too hot but it was apart last year for inspection and it's all good so I'm a bit happier with it over 200 now. It's been like this for three years now but not really high milage.

Not many people seem to run cylinder head temp gauges as I've asked before and not had much of a response but I'll watch where this goes.

Rich

That's reassuring that someone is getting similar temps. I did wonder if the rapido is running cooler because it uses an augusto 6000, don't know if it would make a difference, although the set up is better. I'm guessing that a RB could maybe run hotter than an iron barrell but not sure hopefully we'll get some more feedback.

I fitted a CHT to a RB230 and did a lot of road testing on it. If the sensor is under the plug then I got similar readings and felt that it was getting on the verge of too hot at 210 degrees C. At 200 the engine was running fine.
On Dave Workmans Rally 200 with a SIP speedo the readings were 180 when the engine was pulling up a hill but this was making much less HP and on a cast polini barrel.
I think CHT gauges are useful if used in conjunction with a good ear for how your motor is running because they are slower to relay overheating then maybe a EGT.

Someone put this up in PDF format some time ago.


temps by Bilkers, on Flickr

Cheers, a good guide.

I use a mrb cht gauge on my rb22 with franspeed race, tmx 35 with cam lam powerjet at 65 it's at about 160 170 degrees if held at 75 80 for a few miles it goes up to almost 200 degrees

Rapido 225 , 30mm Mikuni, jl3, agusto 6000,vapor cut under plug gives me between 170 and 190 @60mph (GPs) I did see it rise to over 200 after a fill up recently then drop back to normal after the next fill up though ....

Ts1 225, 35tmx, devtour, gp200 gearing, as it hasn't had a decent clutch in yet (rocho going in this week hopefully) to be fair I haven't ranted it full whack as I can't!

My cht (koso with rev counter) and EGT (light aircraft cheap make) seem to be around 150c tops (?) CHT and around 675, although it has got to 700f on the EGT!, I tend to back off once it goes over 600 to be fair.
I think the egt must be over reading as I should be melting the engine by then surely?
I will be dumping both gauges to go for the simplicity of the sip digi speedo which has the CHT indication there.

I think there's also a difference in CHT temps depending on whether the probe is sunk into the head or is a plug attachment (as mine)?

Anyway as soon as I have the new clutch in it'll be back down to Paul Bakers for a full dyno and I can then see what's what hopefully.
The guide is handy though but worries me.

Not sure if this helps but heres is some data downloaded from my sprinter, top scale is rpm, middle EGT & lower CHT, from the start of a run full tilt so to speak, the EGT goes to around 600 deg C at 9,500 but the CHT goes up from around 180 - 200 and stays almost level with a couple of blips on the run down.

Pete