Hi there I'm new here
I have detonation problems the bike is an independent Chopper came with a six speed revtech, 100ci revtech I blew it up, and I put a 88 twin cam 99 motor out of a Dyna Low Rider / Used stock mileage unknown
Also I installed Thunderheart standard ignition system or module, a dual fire coil and replace cam bearings and the cam chain tensioner pads. By the look of the pads I would say about 20 to 30 thousand miles
Now the carburetor it's a Mikuni I thought 42mm off the revtech but it had a CFY2-96 needle jet, witch is for a 45mm so I bought a CFY2-97 so I thought.
He actually gave me the CFY15 - 97 witch is for a 48mm Mikuni
What noticeable difference in performance
So I determined the carb is a 48mm Mikuni by the needle jet size
The needle jet for the 48mm is longer than for the 45 or the 42mm Mikuni
Currently it runs good except I have detonation at like 5/8 of throttle now I messed around with the Jets the pilot Jets and Main Jets
Currently I have a 25 pilot jet a 97 needle jet set on the 1st clip and a 165 Main Jet
The ignition is set on 2
The bike runs pretty decent it pulls good
Yesterday I sent the ignition up to number six and it ran a little bit better and then the detonation part not as bad but still there
Unti 2500 to3500 rpms I do not have tach bout 5/8 to 3/4 of throttle I want to say detonation if I stay on the gas it'll get through it and start pulling again.
I think with the 27.5 pilot jet it the 97 needle clipped on one with the 165 Main Jet runs bit better than it's running now.
When I put the 96 needle in it. It seems to run worse doesn't matter where the clips is in the middle or the top.

And also seems to me it's really in between the second circuit and the third circuit I guess where they overlap is where I'm getting detonation or something I just need help I'm tired of chasing this I've never tested riden my bike so many times and I put a lot of different configurations and as far as my needles and pilot jets it seems just to move the detonation up and down RPMs a little bit or the throttle to say.
And runs worse
Also when I lean out the pilot jet backfires a whole lot. Enrichen it the backaway goes away on decelerating
No vacuum leaks at the base of my cylinders or the intake or back of carb.
Any help in the right direction I'd be grateful or should I learn how to make a custom ignition map curve

 

1n other thing Im not running with VOS on it

 

Have you tried adjusting the accelerator pump. The screw on the out side adjust when extra fuel will start. The smaller the gap the sooner you will get extra fuel which should help you. Rule of thumb is to start with the gap set to the width of a nickel. The top screw adjust when the extra fuel will shut off. Turning the screw out lets more fuel in for a longer duration which should help in the 5/8 to 3/4 position till the main jet starts operating. The needle clip at the top position will cause the bike to run lean all the way around. As you move the clip down the whole range will richen up also.

 

check the manual for your ignition module. It should have a setting for a less radical timing curve. This is for hopped up motors like yours. I was running a dyna2000 had to set it to the 3 curve with a VOS that opened up later (higher PSI) then my pinging went away or was greatly reduced.

 

I recommend a VOES for a street ridden bike. To stay on the retard curve while cruising is putting heat in the engine. This condition plus roll on can create detonation issues.


What is the plug gap? I would shoot for .035-.032


Most ignition modules have their curves set up in pairs. Same max timing but one will be more aggressive than the other. Meaning the timing will ramp in quicker. Usually both will feel the same but roll on is where difference is.


good luck

 

Get the right needle. A too long needle will starve fuel near WOT. It may be limiting what the main jet can flow. From what I've seen compared to CVs and SnS carbs, the miks cause more popping out the exhaust. I suspect it's due to air leaking arround the slides. That was a common issue with older round slide carbs. My 131 has a 48 on it and has some decel pop. I've not used the TH ignition for a TC but adding the voes will help with decel popping as the timing will be advanced with the throttle shut down.. Pinging could simply be too much timing but I would get the right needles first or go back to the 96. It should be OK except mileage will suffer.

 

Yoy have not mentioned anything about what pipes you have on it and that will influence your carb set up. TC 88's were just fine without voes,,,,but if your ignition is an evo set up, you might be able to adapt it to some mild benifit, but i dont think i would spend the time. Are you sure that your replacement engine is stock? I have found the combo of 22.5 slow and 165 main to work very well on lot of set ups, depending on pipe. I would say you need to get an idea of what kind of compression and cams that you have, then get your timing in order, if you have to biuld a custom map, you might have too......evo and tc 88's timing van be pretty differnt if you look at some of the maps and plots...figure out your comp, then dial in your timing.
M

 

TC88s don't have voes normally, as they have the map sensor.. I just looked. The Tmax does not have Voes.

Assuming it's this one. download the instructions..

ASM5012 Twin Cam Stand-Alone Ignition

from here.

https://www.thunder-heart.com/shopco...p?type=Support

It does look like the curves are adjustable so you can dial the curve back.


IMO a DTT ignition would be a better choice adding the MAP.