Do i need a hotter spark plug?

[06_hondatrx_400]

So i put a 440 big bore kit into my quad. And im rejetting it with an fmf 170 main jet with the air box lid removed. Right now i run a NGK DPR8Z. Would i need to run a hotter plug then that or what kind of plug should i run?

[rooster300ex]

Naw if its runnin good I would just run the stock one.

[speedfreek]

Only real way to know is to do a plug chop.

[06_hondatrx_400]

And how exacally do i do a plug chop? Also do you now what type of octain booster i should run, or have any recommendations? Thanks

[speedfreek]

You need to do a compression test and tell me how much psi you have and I will tell you what octane to run.

Do a search on the plug chop, I am eating and don't have time to explain it, but it's very easy though.

[rooster300ex]

If your not running over 11:1 compression 91 will be fine.

[440exhondaman99]

with your exhaust cam and 440 kit.... 170 is to small it will run lean... i just did the 440 kit with 12.1 piston and a stage 2 cam... you need to run atleast a 180MJ or porbly a 185MJ and a 45 pilot jet.... put them jets in and run it for a little bit and then go from a stop and do a wide open first threw 5th top speed run and once you hit top speed pull in the clutch and kill the motor and coast to a stop.... then take your plug out it should look like the color of card board... if its black you can go with the next step hotter plug OR go down 1 size on you jet and then do it again till you get it to look like card bored... if its lighter brown then cardboard then its runing to lean and you need to go with the next step biger main jet

[06_hondatrx_400]

440 ex hondaman99 i now what ur saying, but i dont think i need to run a bigger jet cuz i talked to a carburator specilist from the brand of jet kit im using and he said what i have in for jets is the best possible set up i can have. The jet sizes with the fmf are different the others, so thats just what the guy said to me.

[440exhondaman99]

well i ran a stock bore and a 11.1 piston with stage 1 cam for a while with a 170 main jet and it ran good and was jeted perfect... but when i instaled the 440 kit i ran it with a stage 1 cam and it ran ok probly could of been bumped up 1 size on the MJ to get better top end... but once i put that stage 2 cam in i lost almost all top end and it was runing a lil lean so i bumbed it up to a 185 and 45 pilot jet and the motor came back to life more on top end.. if you ask me i think your starving the motor for fuel a lil bit since you got all the upgrades... but i gues run it that way and do a plug check... im geusing its guna be lean... id rather run it a lil ritch to keep it cooler because that motor aint guna blow near as easy ritch then it will lean

[440exhondaman99]

i see your runing a powerbomb header.... what do you think of it??? do you feel it maid more power??? and your runing the same slip on that i am... i sugjest to cut that slip on down 3 1/2 inchs.. it maid a difrence with mine.. wasnt realy louder it just maid more power that way... those slip ons acturly make your bike lose power and i think that was the reason why because there so long.. cut it down and see what you think i like it better this way for shure.. but i wana know what you think about that header cuz i got one on the way.. the guy i was ordering it off of said i wouldnt be able to tell a diference in power or anything

[06_hondatrx_400]

Well i havent acually got the header yet, that was just on my list of upgrades then i kinda ran out of money so yah. And as far at the spark plug its not running lean its acually running on the richer side. thats y i was wondering if i need to run a hotter plug.

[fearlessfred]

u should do the plug chop as descibed there are to many varibles like altitude for one to go by what someone else has .it can be a good starting point . then jet as descibed u would almost never go to a hotter plug if u have raised compression the heat range of a plug is the temp that the plug is and has nothing to do with spark . by raising compression u have already raised combustion temps .i have always ran the coolest plug that wouldnt foul but maybe i dont know what im doing

[06_hondatrx_400]

I now what your saying it makes sence. But anyways today i had to replace my throttle cable and i was messing with my card a little bit and i found that my choke was on just a fraction of an inch, and i think thats what was causing it to run a little rich. But yah im deffintly going to look into doing a plug chop and see what the resaults are.

[fearlessfred]

yes i would definitly do the plug chop than . and if u can run a cooler heat range on the plug i would good luck to u

[440exhondaman99]

Originally posted by 06_hondatrx_400
I now what your saying it makes sence. But anyways today i had to replace my throttle cable and i was messing with my card a little bit and i found that my choke was on just a fraction of an inch, and i think thats what was causing it to run a little rich. But yah im deffintly going to look into doing a plug chop and see what the resaults are.

i read a post about removing your choke completly and it will give you a lil better flow... wont be much but will be a lil better... but if you do this you most deflently need to up grade to atleast a 42 pilot jet... that will fix your cold start problem completly... your probly thinking remove the choke no way... but put that 42 pilot jet in first and run it a few times from a completly cold start and dont use the choke you wont find your self needing it at all then once you see that you dont need it remove it for a lil added flow.. its realy easy.. just make shure you fill the hole with somthing... i wont go back to using a choke on mine so i JB welded the hols on both side so its completly flat for the best flow i can get... you do that and you wont find your choke sticking anywhere but to the trash

[06_hondatrx_400]

Okay so say i deside to remove the choke. were would i get a 42 pilot jet?

[440exhondaman99]

Originally posted by 06_hondatrx_400
Okay so say i deside to remove the choke. were would i get a 42 pilot jet?


goto any local dealer that sells parts.... tell them you need a 42 pilot jet for a kethin carb.. they are 5 bucks.... i started out with a 42 and i went with a 45 today because i have the big bore and all the goodies and that 45 helps with off line power a lil bit that i felt

[06_hondatrx_400]

Yah theres a honda dealer around here. Well i have a 440 big bore two with alot of stuff done to it so i would be better off running a 45.

[06_hondatrx_400]

hey 440exhondaman99 i see in your signiture that you have a 440 big bore and you are running a 2 degree timing key. I am thinking about doing this to my quad and i was wondering how you liked it what is the power gain like. Also do you notice acessive heat from the key or not. Thanks