if you have installed a 1250 kit and have a carb. what size main jet did you use...I have the kit plus N4 cams and 1200 valves, open air filter and short shot exhaust, dyna ignition....and I am getting a fair amount of pinging/detonation when the engine is good and warm (20 minutes on highway etc.) when I accelerate pretty hard between 70 and 90 mph and if I shift a little to early at lower speeds....right now I am running a 180 main and I can't remember the low jet # but I went up I think one size....there are no vacuum leaks and I have increased the back pressure on the exhaust just enough to help it run better at low rpms..... i up until now not been running it hard because I have been breaking in the new parts, so I don't know if this is new...also I have been running 91 octane ...SOOOO, what to do first, carb jet, or change timing, different plugs or what....Oh and that bike runs like a scalded cat...

 

Who did your kit? And a 180 main sounds too small! Hammer recommends a 45/185 combo for the standard conversion. I don't have mine together yet (within the week), but I'm starting with the 185. I have Impact head porting (still keeps the stock 883 valves), and I'm thinking I may need to go up a size in the main jet after I get it on the dyno. Time will tell. From what I've heard that 45/185 is pretty close for all but the higher builds.

Also, pinging is usually ignition related. Everything else can make it worse/easier to happen, but ignition timing is usually the main culprit. Which dyna ignition are you using, and what settings?

Also, please give me the more detailed aspects of your build. Year and model of original bike? Level of headwork? Squish clearance? The more info you can provide the better.

 

45/185 when I had a keihan

running a 28/170 with the mikuni

30 degree dome piston
1.770/1.530 valves
V4 cams
Dyna 2ki ignition
screaming eagle coil
Mikuni 42 carb
Here is the headwork as received from Hammer yesterday after He rebuilt my destroyed heads
Before

after

 

Whoever you got your kit from should be able to advise you on suitable ignition timing and carb jets, to get you close to a good running engine. Having done that I personally would get a dyno tune, after running it in for a decent mileage.

 

I have the kit from NHRS and the ignition is DYNATEK 2000i, head work done local (ported and cut for big valves)...year 2000 hugger..don't remember the squish, but when I checked it was tight but within specs..

 

The Hammer recommended 45/185 was spot on for my build, (info in sig).

 

Sounds good. My only concern would be with the local head work. You'd have to make sure what the chamber CC'd at to make sure your compression is good. What pistons do you have and what is your compression ratio?

Another thought is to make sure your VOES is working right since you said it happens when you roll on. Normally the VOES will retard the timing at roll-on and heavy load so you don't ping. If you didn't adjust the VOES it is possible it is not switching soon enough.

With the stock switch, it is set for 3.5-4.5mmHg for the switch point. A modified 1250 with high compression can pull this vacuum better than the stock bike and cause the VOES to not switch on roll-on. This would give you ping at the situations you described.

You can adjust your VOES by removing the plug and screwing it in/out (can't remember which way is which since mine broke so I just bought a different one) to change when it switches, or you can buy one that is set for a higher vacuum level. I'd suggest about 6mmHg as a target if you go the new route.

 

the only head work done was the porting and bigger valves, the shape of the combustion chamber was not changed and the compression is 10:1...and it seems to me that the spark controller can be adjusted to work around the VOES (I could be wrong as I don't understand exactly how it works)....I think the first thing I am going to do is up the main jet to 185 and see how that changes things, I just bought a 185 and 190 main jets, so when they come I will play with them for a bit first..then I will toy with the timing...

 

this the kit I used http://www.nrhsperformance.com/ekit8831200.shtml ...along with what are basically stage II heads...I didn't do new springs etc. because I was not going with hi-lift cams...

 

Yeah, shouldn't be having those issues at 10:1 with N4 cams. The jetting could help, and make sure you're using Curve 4 (least aggressive) on the 2000i.

I'd recommend a properly set VOES, but you can always run without. You just lose a bit of the efficiency when cruising easy from the extra advance.