Why...

[400exrider720]

why does my atv still run now that I put on the HMF silencer? I didn't change jets at all. Most people say you have to rejet. I checked my plug and it is a little black but not too much to worry. Thanks for the help.

P.S. Also HMF silencers sound awesome!!!

[Scro]

It will still run, but it won't give you any more performance. In fact it probably hurt it and you didn't realize it. Bump up the main jet and you should really see the gains.

[H400exRacr]

you deffinetly need to rejet it.......it will run fine without doin it but once you rejet it you will notice a significant power increase and you wont have to worry about your engine being harmed by improper amounts of fuel in your cylinder

[LT250RMan]

If your plug is BLACK looking dont bump up a jet size that will make it run richer, you have to go down a size so your not running rich and you will gain more power because your not over fueling your engine, but make sure you dont go to lean because you will cook your engine. When you rejet you want your plug to be a nice light chocolate brown color but make sure its NOT a yellow or a white color that means you have it jetted to lean.

[400exrider707]

Originally posted by LT250RMan
If your plug is BLACK looking dont bump up a jet size that will make it run richer, you have to go down a size so your not running rich and you will gain more power because your not over fueling your engine, but make sure you dont go to lean because you will cook your engine. When you rejet you want your plug to be a nice light chocolate brown color but make sure its NOT a yellow or a white color that means you have it jetted to lean.

Wow:huh First of all putting a pipe on and leaving stock jetting isn't a great idea, but now you tell him to go down in jet size??? His plug is black because he probably left the same plug in, instead of buying a new one and doing a plug chop like he's supposed to.


Bump up your main to a 150-152, pilot to a 40, and move the clip on the needle down one spot.

[firefighterjosh]

Did you install a new plug after installing yer pipe? If not that is y it looks good.

Example:
My buddie put a FMF Silencer on his 400. He never rejetted. Ran good. After some hard riding and 6 months later. What do you know blue smoke. Then Ca boom! Piston had a hole burnt in it and bent 2 exhaulst vavles and put pits all over his head.

Lesson:
Yes your quad will run for a while but eventually it will blow. If he would have just taken 10 Mins to rejet and check his plug he wouldn't have had to fork $700 over for a new engine.

[LT250RMan]

when i read his post it sounded like it was running rich because he said the plug was black, but now when i think about it hes getting more air flow with the aftermarket exaust so its probaly running a little on the lean side. I find that its harder to tell if the engine is running lean with a new plug because the white or yellow color that it would be if its was running lean would be harder to see on a new plug because a new plug is already a light color(grey).

You dont have to put a new plug in to see if its running lean or rich, if the plug has some black carbon on it the yellow or white color will show up way more on a black plug (if its running lean) than it would with a brand new plug, when i rejet my snowmobile for the mountians i dont buy a new plug every time i change jets because i find it harder to tell if the engine is running lean with a new plug because the plug is a light color already and plus it takes more time for the color to show up on a new plug.

[firefighterjosh]

R u Retarted? Seriously........I am not even going to argue I will let somone else do it:huh :huh :huh :huh :huh

[LT250RMan]

Ok then explain to me why you need a new plug when you put on a diffrent exaust? Think about it a light color does'nt show up that good on a light color. I have rejetted my snowmobile LOTS when i go to the mountians and i never go buy a new plug just a change my jets and i have NEVER had a problem EVER.

You must think your cool calling people a retard on a computer only little kids do stuff like that.

[firefighterjosh]

Originally posted by LT250RMan
Ok if your calling me a retard then explain to me why you need a new plug when you put on a diffrent exaust? Think about it a light color does'nt show up that good on a light color. I have rejetted my snowmobile LOTS when i go to the mountians and i never go buy a new plug just a change my jets and i have NEVER had a problem EVER.

oh ya you must have no life if you call people a retard on the computer.

Well I don't want band so I can't call you What I want to Anyways...

Do you know why the plug turns white??? Prally not.
It burns white...the engine runs hot turns the plug white.

You install a new plug cuz you want a accuarate reading.

Edit: Just wait his plug will turn white. It prally isn't running real lean....but it will turn color in time, It has to burn off all that build up that was already on there.

I am not about to get into a big debate. I know and everyone else on this site knows, just wait ppl will be on my side. If you would listen maybe you will learn something.

[LT250RMan]

Originally posted by firefighterjosh
Well I don't want band so I can't call you What I want to Anyways...

Do you know why the plug turns white??? Prally not.
It burns white...the engine runs hot turns the plug white.

You install a new plug cuz you want a accuarate reading.

Edit: Just wait his plug will turn white. It prally isn't running real lean....but it will turn color in time, It has to burn off all that build up that was already on there.

I am not about to get into a big debate. I know and everyone else on this site knows, just wait ppl will be on my side. If you would listen maybe you will learn something.

you could have said that in the first place insted of calling me a retard buddy!! and i know why the plug turns white i stated that before that if its white or yellow color its running to lean, i have been working on snowmobiles and quads and cars ever since i was about 12 years old so i know how to check to see if the engine is running lean or rich. I got to the mountians on my snowmobile more than 3 times a year so i know what i'm doing because if i didnt the engine in the sled would be cooked.

[firefighterjosh]

Originally posted by LT250RMan
you could have said that in the first place insted of calling me a retard buddy!! and i know why the plug turns white i stated that before that if its white or yellow color its running to lean, i have been working on snowmobiles and quads and cars ever since i was about 12 years old so i know how to check to see if the engine is running lean or rich.

Well I read your 2nd post again and I noticed you did stat that It was running lean. "but now when i think about it hes getting more air flow with the aftermarket exaust so its probaly running a little on the lean side" I apologize for reading that wrong.

But this"You dont have to put a new plug in to see if its running lean or rich, if the plug has some black carbon on it the yellow or white color will show up way more on a black plug (if its running lean) than it would with a brand new plug"

Is what got me. :ermm:

[LT250RMan]

Originally posted by firefighterjosh
Well I read your 2nd post again and I noticed you did stat that It was running lean. "but now when i think about it hes getting more air flow with the aftermarket exaust so its probaly running a little on the lean side" I apologize for reading that wrong.

But this"You dont have to put a new plug in to see if its running lean or rich, if the plug has some black carbon on it the yellow or white color will show up way more on a black plug (if its running lean) than it would with a brand new plug"

Is what got me. :ermm:


well when i change the jets in my sled i rarely put in a new plug because I find it harder to see the white or yellow on the new plug because the plug is a light grey color and i think the white or yellow color shows up better on a darker plug but i guess thats just the way i do it.

[400exrider720]

"Did you install a new plug after installing yer pipe? If not that is y it looks good."

No but I did clean the spark plug so it looked almost new. Then I went riding for a couple of hours and it came out black.

[GPracer2500]

http://www.exriders.com/vbb/showthread.php?s=&threadid=237664