Compression numbers and pinging

[Guest]

So, I did my first compression test after my rebuild ~1000+ kms done so far. Got 150-160 psi from all, one of them required a few more cranks to get to 150. All dry.
On one of my last rides I noticed a new noise at 7k- redline, but I couldn't pinpoint it. I thought it may be pinging
From my auto days, pinging usually occcurred at lower rpms when you stepped on the throttle. Could I be getting pinging at these rpms (if my main jet is too small I am thinking) I havent done high rpm plug chops lately, since I installed my new carbs. I am a bit worried cause I dont want to break or burn something. I have a 137.5 mikuni main on the 34mm carbs. Plug look real good and tanned.

[posplayr]

I just did the 1168 kit, and so got my feet wet with CV's and jetting. Chef was backing me up all the way with help from Rapid Ray at the Julian base camp .

You should be able to pull hard to red line otherwise the jets are not right. That is the first step. Your needles don't matter till it pulls strong to 9-10K (what's redline ).

Another thing is I had to run Premium with the 1168 kit at 10.25:1 .

Make sure your ignition is in good shape. I did the Coil relay mod to power my Accel coils Dyna S as well.

I has bobbling at high RPM and MID RPM at different time. It seems to be much different that cars (at least in my experience).

For a while I was wondering if we would get it sorted. Now it purrs.

JIm

[chef1366]

Take a pic of the threads of the inner two plugs. If you have color on the threads above three threads go up on the mains. Maybe even a 142.5. Start rich and work lean. As I said before I almost melted a head trying for peak performance instead of keeping an eye in combustion temp.
Are you running a stock ignition? I forget.
Also if you are running high compression pistons you need to run high octane fuel.

[gearhead13]

Thanks for the replies, guys. I ALWAYS run premium 94 octane. I have color maybe 6 or 7 ? threads up on the plugs
It pulls real nice n' hard right from 4k rpm up to and past redline. I have the dyna coils with coil relay mod and stock ignition. The next set of mains I have are 145's. I will drop them in and see how it runs, at least it will give me an idea. People tell me 137.5 is way rich now, oh well what do I care what they think, eh?

[chef1366]

With six to seven threads you are asking for trouble.
I have some jets I can send you. PM me

[gearhead13]

Thanks for the offer, Chef. I put in a set of 145's today, and it runs pretty good, not overly rich or anything. Actually if my butt dyno is right it is making better power. Checked a plug when i got back and they look the same, would have done a plug chop but pretty hard to do at rush hour.

[TheCafeKid]

Im still learning my carbs, but i just dont see how you can be lean pushing an 816cc mill with 34mm carbs at 137.5 main jets. Thats bigger than what im running in my 1100...

[chef1366]

Im still learning my carbs, but i just dont see how you can be lean pushing an 816cc mill with 34mm carbs at 137.5 main jets. Thats bigger than what im running in my 1100...

Ported head and cams

[chef1366]

Thanks for the offer, Chef. I put in a set of 145's today, and it runs pretty good, not overly rich or anything. Actually if my butt dyno is right it is making better power. Checked a plug when i got back and they look the same, would have done a plug chop but pretty hard to do at rush hour.

You'll need new plugs to check the heat range with the new main. Once the threads are heat colored it's there to stay.

[posplayr]

Gearhead

So what was done to the head? How far oversize on the valves?

My 1168, ported head with 28/23 mm valves (95 cfm flow at 0.340) is running 145 and seems quiet happy with about 2 rings of heat.

Bill with nearly same motor but 28.5/23 valves (less radical port job) is now running 152.5 1-2 rings of heat now (Bill to confirm)?

So seems even with the same valves and engine(carbs, cams, pistons) , the port job is making a difference.

Bill and I still need a show down where hopefully I'll stay in gear. Bill be forewarned if we get to redline in 3rd I'll probably back off

Pos

[chef1366]

. Bill be forewarned if we get to redline in 3rd I'll probably back off

Pos

I won't

[posplayr]

I won't

Yea I know

[gearhead13]

The valves are stock size with a back cut. I worked on the head for a few weeks on and off removing unwanted aluminum from the ports Not hogged out, just nicely smoothed out and radiused.
The idea of putting a larger carb on a smaller engine makes it so there is less of a signal to the carb fuel passages, making it need a larger main to let in enough fuel with the lessened signal to the main jet. (my assumption)
That said, it is really hard to tell, but it could go to a 140 or 142.5 and be happy. Doesnt seem to wind out as fast on the very top, but lots more in the midrange. I will go and buy some new plugs and drop them in. How long til the plug threads are colored again?

[posplayr]

Doesn't seem to wind out as fast on the very top, but lots more in the midrange. I will go and buy some new plugs and drop them in. How long til the plug threads are colored again?

Maybe someone will chime in (Bill how are the Lakers doing) but you need to 1.) get a strong pull to red line then leave the main ALONE and 2.) then and only then move on to the needle. In other words don't worry about mid range till you have it pulling strong to red line.

The Factory pro directions for CV;s said this pretty much exactly. So unless you go back and fix that you will be futzing Posted here just last week.

Jim

[chef1366]

I have some 142.5s and 140s if you want to try them.