spark plug questions

beerock · 06-03-2008, 9:27 PM

I just was reading through the manual and the rc51 coems with a ifr9h11 ngk plug. for colder riding the manual specifies a ifr8h11 plug.

from the first experience i ever had changing a plug on a dirtbike(a honda 1988 cr80) i went form a ngk br9es to a br8es and WOW what a difference the plug change made.

im curious if anyone else runs the hotter plug in there bike?

cbr900racer77 · 06-06-2008, 5:02 PM

I will probably get flogged for saying this (but it's the truth)...HOW you ride is what determines the heat range of plug. If you putt around town at lower rpm's a hotter plug will be helpful. If you stay near the redline more than you do idle then a colder plug will help. I've seen people go with a hotter plug because they are running rich...I tell them to rejet the thing the RIGHT way and it will run fine.

beerock · 06-06-2008, 6:04 PM

Quote:

Originally Posted by cbr900racer77

I will probably get flogged for saying this (but it's the truth)...HOW you ride is what determines the heat range of plug. If you putt around town at lower rpm's a hotter plug will be helpful. If you stay near the redline more than you do idle then a colder plug will help. I've seen people go with a hotter plug because they are running rich...I tell them to rejet the thing the RIGHT way and it will run fine.

kudos to you sir!!

your right rejetting is a better answer. there is somehting to be said about a hotter range plug though. like i said on my cr80 when i changed the plug form a 9 to a 8 it made a huge difference to the bottom end. so im wondering if it would help the bottom end on a rc5 and then remap the top end for the hotter plug(more fuel)

cbr900racer77 · 06-06-2008, 7:31 PM

That's a good question....Do you have access to a dyno with a wideband? I'd like to see exactly how a different heat range plug affects A/F. On a sidenote, a buddy bought a 51 and let me ride it one time..OMG, that thing was scary fast. I would have NEVER thought a twin would move like that. It would power wheelie at the flick of the wrist, didn't really matter what gear you were in (btw, i'm a punk when it comes to wheelies, that's why my RR is stretch 12"

)

beerock · 06-06-2008, 8:19 PM

well here is what I found out per conversation with a retired factory honda r&d engineer. first off there race motors were high comp so they ran colder plugs, however they always had there motors on the brink of destruction tuning wise. so in other words a company may say you need a heat range of 10 for a high comp but thee own race motor would run a 9 or maybe even a 8 if they could get away with it. another words, dont always believe what you read.

He pretty much said that if we ran a 8 heat range we would get more bottom end snap with the 8 plug. he did say make sure you keep an eye on your temps.

furthermore, you could gain even more power out of the motor by running the 8 heatrange and richening up the maps profile. OBVIOUSLY this would mean less gas mileage. but hey its give and take. power or economy?

so yea from what he said there is def a gain to be had by using a 8 heat range plug instead of the 9 heatrange.

he also told me a funny story about how honda would put there cam specs in the manual for the 600's so ama wouldnt have to look at them. BUT the cams in the 600's WAS NOT the cam specs in the manual....

so, would this mean they did the same with the plugs?

im tempted to try it out.

lastly he asked if i was using ngk's i said of course he said good. so stick with ngk's when testing.

btw this cam be done to any bike to gain power so long as you keep eye on the temps and theres no audible pings