Scooterotica

Looking for temperature readings on cylinder head on an rb250 if anyone has this info.
I am running between 135 and as much as 175 is this normal..

Sounds a bit low to me.

I have a Taffspeed RB250, in top at about 70mph (7000 rpm) or above it's usually about 220*c - 230*C, thermocouple on the head to a Michron 4 tacho.

Had it apart a few times over the years and all seems good, I don't think there's a lot of info on head temps, it seems those interested in temps use EGT's.

This pic was posted on here some time ago for reference.

Rich

All the experts thoughts tend to say 200c is very hot but my rb 236 regularly goes over 230 ish and hasnt gone pop, and temps depends greatly on road & wind conditions. I think some chts read higher than others. If u look at the rotax chart in the above post it shows 250c as acceptable. But its all about knowing ur own engines speeds and temps. Get out and ride it then u will discover how it runs and what temp speeds it can do.

JPO200 wrote:Looking for temperature readings on cylinder head on an rb250 if anyone has this info.
I am running between 135 and as much as 175 is this normal..

same-as i get on my vapour for rb230 but running a super monza piston and head to suit which am told makes them run cooler i personal think if gauge anyone is using shows over 200 and is corect reading few miles at this its gooner blow hole in piston--i-done-2-mb-pistons due to heat

rbgaz wrote:

JPO200 wrote:Looking for temperature readings on cylinder head on an rb250 if anyone has this info.
I am running between 135 and as much as 175 is this normal..

same-as i get on my vapour for rb230 but running a super monza piston and head to suit which am told makes them run cooler i personal think if gauge anyone is using shows over 200 and is corect reading few miles at this its gooner blow hole in piston--i-done-2-mb-pistons due to heat

If you have done 2 MB pistons in your RB230, then maybe you should have been asking the person who built it what had caused the engine to fail?
Without knowing what caused the failure it will happen again & again!

What can I say is that Richard's RB250 (22/2) has been runing for about 4 years now, has 32bhp & has run over 220' up to 280'c with no screw ups!
One of the major improvements in cooling was to get Richard's RB flywheel cowl to fit within 2mm of the fan.
He had an AF flywheel which was about 12mm away from the cowling due to the short fins. It dropped approximatly 30'c off the running temp.
He is now planning the fitting of a retarder unit, reseting static timing to improve the low down performance which is not bad to start with.
RB motor development goes on!

If you use a CHT unit the the following may be of interest to you.
A maximum head temp of 210'c gives you the grade of spark plug to use BR7ES or BR7EG-V or N4G
A maximum head temp of 240'c gives you the grade of spark plug to use BR8ES or BR8EG-V or N3G
A maximum head temp of 280'c gives you the grade of spark plug to use BR9ES or BR9EG-V or N2G

Also remember to gap the plug to 0.020" or 0.5mm as the CDi KV output is not very high & forgetting to do this will end in the plug misfiring under load when too rich a mixture is set!

Set your working corrected compression ratio to below 6 to 1 allowing the use of 95 unleaded fuel & oil mix.
Remember that your fuel also cools the motor as well as lubricating it!
As the summer heat wave is now hear the differance in air to cylinder temp will be much less so possible problems to come!
Thats why the Indian Flywheels have longer fins to increase air flow over the cylinder!
It gets much hotter in India than here & they only had 10bhp to cool down!

Best regards to all

I imagine that all cht gauges are differing in their readings if you done a back to back comparison.

For the record my gauge from skydrive reads about 220 degrees when doing sustained high speed cruising and i imagine the motor could survive runnin a bit hotter .

rbgaz wrote:

JPO200 wrote:Looking for temperature readings on cylinder head on an rb250 if anyone has this info.
I am running between 135 and as much as 175 is this normal..

same-as i get on my vapour for rb230 but running a super monza piston and head to suit which am told makes them run cooler i personal think if gauge anyone is using shows over 200 and is corect reading few miles at this its gooner blow hole in piston--i-done-2-mb-pistons due to heat

I use an augusto 7000 on mine at the minute, It runs hot at low revs like round town around the 120 c -140 c area when pootling but runs cleaner at low revs.

Gud post Ian lots of gud stuff in there. I was a bit wary wen my rb started to go as high as 180 -190 c when only doing around 60 mph but I got used to it and no I dont panic until it gets to 230c thats when the light comes on on my vapor speedo, I also think they will run hotter as I have seen my temp guage go as high as 250c once, I pulled in the clutch and let it cool down and all was well, so I know it can go that hot and not blow up, altho I shall not be trying to repeat it.

I believe that AFS are a little over cautious in theyre temp guidelines etc and who can blame them, when things go wrong the first place most people look at is the dealer or manufacturer of the parts and thats not always the case.

In my opinion they are one of the best dealers in the country, helpful, reasonably priced and always have time for you,

They are soon going to be trying out the Avanti cyl head on the rbs to try to get the cooling a bit better, I hope it works as cooler can only mean faster for longer!

As u say Ian "RB motor development goes on!"

I should clarify that my T/C is fitted under the plug rather than fixed to a fin on the head, I would imagine that this would make a significant difference to the result.

The trouble with having a gauge is that you become obsessed with watching it and it can detract from the enjoyment of riding your bike, if it is set up well you should only take notice if it moves away from your normal range, although you need to know what is normal.

Keep us updated, it's all interesting to me, as it happens this RB motor of mine is probably the best motor I've had in 25 years of riding tuned lammy's.

Rich

Have to say Eric Cope has been using the Avanti for a long time now with great results :fb: If you cant beat em join em :fb:

Hi Jason

This graph shows our RB sprinter temp data, at full tilt ie 9500 rpm the peak EGT is around 600 deg C and the CHT fairly stable between 160 to 180 deg C and only goes over 200 at the end of a run when your off the throttle.

Pete