Hi, been a while. I’ve had my tc88A recently rebuilt at 180000 km. It now has a S&S 4 3/8 crank wiseco 9.6 forged flattops,my barrels bored to 95”,my stock heads cleaned up with new exhaust valves and beehive valve springs. I’m assuming it has a stock head gasket. I’m running se 211 cams,a 42 mikuni hsr and a Vance and Hines pro pipe h/s. It’s putting out some pretty decent torque and power at 96hp and 105lbft of torque,on the builders dyno anyway. This builder dyno’ed using the stock 160 main jet stock 97 needle 20 pilot 70 accelerator pump nozzle with the needle clip position 1 notch leaner to improve the cruise economy. I have since tried some different main jet sizes and at the moment it has a 167.5 in it. I also have a twin tech ignition which I’m never quite sure if I’ve got it set right. The reason for all my concern with the tuning is the motor has a tendency for spark knock,especially top gear roll ons up gradients and even around the 120 140 kph mark. It has been suggested that I only run 98 fuel where as I only ran 95 in the past. I took it for a run yesterday up the same hill around the same speed and with the ignition set at 1 initial and 2 advanced still pinged when cracking the throttle, although only lightly. I have no idea what actual compression this motor would be putting out ,and any thoughts would be appreciated. Also the builder had the ignition set on 2 initial and 5 advance. So is it my ignition settings or carb settings or both? Maybe I’ll just have to live with it😂

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Thanks for replying John. I’ll take your advice and and throw my info at the mob you suggested and see what they say. I’ve pissed the guy off that built the engine and he’s not very forthcoming with what he did on the build,but no matter. I’ll do a comp test and let you know the figures.98 fuel has decreased most of the knocking but I moved the initial timing back to 2 and the advance back to 1 and this seems to have eliminated 98% of the pinging.

It's just an online calculator, not a service or person etc. It makes it hard without the info. 

No worries👍🏼

Compression would be closer to 9.2:1 with stock chamber heads, and 8.3 corrected.

I'm also a bit confused, you have a 4 3/8" crank, but you mentioned bored to 95" ?

Yes speedster I mean it’s a 103 cube now with the stroker crank and my 88 barrels bored to suit. I ran it over another blokes dyno twice after the original run on the builders dyno, once with the 160 main jet and again with a 165 main and his figures were 96 hp 105 ftlb and 97 hp 104 ftlb respectively. Two totally seperate runs on different machines both on smoothing 5. The bike has good low end and midrange.I’ve read plenty about this cam supposedly matched to higher compression but it seems to work fine in this combo.If my comp is as low as we think then why the need to retard my ignition as much as I have ie. initial 2 advanced 1 to counter pinking in top gear roll ons? I pestered this builder with all these questions, he wasn’t forthcoming with answers so it’s still a mystery to me.

Thanks mate I’ll do that soon and I’ll let you know how it goes👍🏻

Gday Hoody’ regarding the circuit to tune to help eliminate roll on pinking, my needle is the stock 97,one clip position leaner than the stick middle position,needle jet stock,accelerator pump the stock 70. Air filter is a round k&n. Breather has been redirected to ground via a hose . I’ve tried different main jets on a straight road flat out to try to determine correct size that way for that part of the circuit and to me the 160 was a bit lean but produced good power so I thought I would bump up that jet size to be on the safe side. Your opinion is much appreciated. Cheers Gazz.

Put the carburetor back to all stock as supplied, bear in mind float level is a completely independent tune area as well. You may have a too aggressive ignition advance curve installed, that said, you may have.  Get it onto a reputable dyno.

Thanks Hoody are you saying I should run stock jetting and settings on my Mikuni even with a bigger motor than what I had. I had all stock settings on the old motor which was a stock 88 with 203 cams. I have 211 cams now and a 103. Stock 88 head. My dtt settings at present are initial 2 advance 1 with multi spark enabled. Pinging is now only light rolling on up a gradient but it’s still there. Also on these ignition settings I’ve noticed it doesn’t kick back which it did on hot start up’s sometimes. There is some bigger chunks of metal in my primary these days which I’m assuming is bits of starter pinion and clutch ring.

Hi Gazman the guys are right there ,have a compression check.

Yep will do and thanks for your input Uncle. Just waiting for my dodgy back to come right now🙄

Cheers thanks Hoody really appreciate your input,as soon as my cactus bulging discs settle I’ll get the comp test done hot and take it from there.👍🏼🙂

Don’t know if these pics of my dyno reports will be clear.

The report without the a/f is the one from the builder dyno and the other from a mates dyno showing a/f . The blue line on the mates was with a 160 main,and the red with a 162.5 main.