Topic: wiseco 836 kit... is premium gas required?

[amattel]

I've been searching through posts for info about gasoline requirements for the 750's.

It seems clear that stock they are fine with regular gas, however I have not found a specific reference to the wisseco 836 kit.

I have assumed that I needed premium because of higher compression.  Can someone verify this for me?

thanks,

Adam

[MRieck]

You will need the premium.

[eldar]

I thought premium was not needed unless you had the high comp pistons?

[Sam Green Racing]

Eldy, the 836 is higher compression (10.5 to 1).

Adam, you are thinking along the right lines, like Mike says, the use of premium gas will keep the motor a little cooler.

Regards to all Sam.

[eldar]

It is but I was meaning the 12:1 kit that was also made.
Would the higher octane still be needed with electronic ign since the spark is better and timing is more exact?

[Sam Green Racing]

Not knowing what compression Adams pistons are, I passed on my view of what I would use.
If the motor has 12 to ones in it, the bike in my oppinion should be on aviation fuel or methanol.
If it's the bike in his avtar it would seem to be for highway use, that being the case personaly I wouldnt use pistons any higher than  10.5 to 1 and on on premium gas.

Sam.

[eldar]

Premium is pricey so I might just stick with stock. How about midgrade gas? Our midgrade here is 89 or 90 depending on where you go. It is the same price as regular. the average premium is 92.

[Sam Green Racing]

To be honest Eldy, I can't coment on a mid range gas as we don't have one over here. (in fact we don't have gas at all..it's called petrol. ) We only have unleaded and super unleaded.
We use the super unleaded in the race bike,with stock pistons and on a warm day the motor never cools much between each run.
Next years motor is in a much higher state of tune but only useing the 10.5 to 1 836 pistons so as not to over load the crank.
As our old motor holds all the class strip records (except 1) it's no point going over the top with power, reliablity is # 1.
This motor will run Av gas (aviation fuel) as the motor has to have sufficiant heat to function properly but should not allow it to overheat.
If you had to pay the fuel prices we have in the UK you would be very

Sam.

[eldar]

I think you are all getting ripped in the ass (arse) on PETROL prices!
Do you know the octane of your super? I suppose that is done differently as well so the numbers may not mean anything.

[amattel]

Thanks for the input.  I like to verify what I think I know about my bike since so often I am quite wrong

when I had it rrebuilt (cb750k2) I went with the wiseco 836 kit so it would feel more competent overall. and it was the one my mechanic recommended.  MY girlfriend and I love to tour on it and it really does feel more competent both on the highway and in the twisties.

The only reason I was able to afford the rebuild was becasue my mechanic did it "on the side" in between the regular shop work so it took him 3 months to do it which allowed me to save for it. 

At one point  he was on the verge of putting the top end back on and he says, " you know adam, it wouldn't cost you any more in labor if you put a hotter cam in right now."  so, we picked out the web cam 41a as being slightly hotter but not so hot as to seriously reduce reliability.

I had 31mm kehin cv carbs from an '83 cb650sc nighthawkinstalled.  THey were only $41 on ebay and the same one's he used on his cb750 drag bike.  They fit the early k bikes almost right on.  he was able to make up the slight difference with the flexibility of the rubber intake boots.  Throttle response is nice and crisp as compared to the stock carbs.

Adam

[Sam Green Racing]

The numbers dont mean a thing and as I personaly don't use petrol I wouldn't know what octane rating our gas is.
Before we went to all unleaded we had 2 through to 4 star (92 to 98)(RON) this would equate to your 85 to 90(MON) as the way it is measured is different, then to further complicate matters, your 85 to 90 is shown on your gas pumps as 88.5 to 94 octane,(PON) this being the difference between the two methods of measuring the knock rating.
I last bought 4 star for my RS125 about 8 years ago when you couldn't get Av Gas unless you had a airplane.
When we went to all unleaded a lot of people with old cars and bikes got worried over burning the valve seats out with the unleaded fuels.
The way I looked at it, when Honda first started to export bikes it was to the USA who had unleaded then, so the bikes was made to run on this fuel. I couldnt see Honda fitting seats of different materials, they would be made to take the worst that could be put into them.(regular unleaded) We use the super unleaded Shell Optimax in the CR750 with no problems.
The bigest part of the price of our fuels is TAX my car runs on diesel 75mpg, my two small CBs use methanol £8 ($13.76) per gal but do very little milage on the sprint and drag strips.

Sam.

[Sam Green Racing]

Hey Adam,  Sounds like the only thing you need now is to get Mike Rieck to rework your head, it's the ports that realy restrict the breathing of these motors.

Sam.

[MRieck]

Hey Adam,  Sounds like the only thing you need now is to get Mike Rieck to rework your head, it's the ports that realy restrict the breathing of these motors.

Sam.

I'm porting 2 CB heads right now Sam. One street, one race. I'll post some pics so you can get a good view sir.

[Sam Green Racing]

That should keep you out of trouble for a few days.