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Discussion Starter · #1 ·
Im fixing to order my HMF, and was wondering about jetting. Can i get by with just replacing the jet or do I have to buy the complete jet kit? Thanks
 

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Just the jet is really all you need. I assume you have a 500 Foreman,
so the 170 jet would be what you want if you live down south with the
rest of us. Not sure what it would be for higher altitudes.
 

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be careful though, THe 170 is the dynojet size. which means you need the whole Dynojet kit to use it.
you can just replace the stock jet with a bigger jet but i am not sure what size that would be in that manufactors size
 

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Discussion Starter · #4 ·
oh well..

oh well, I just ordered the whole kit, maybe it will be ok. I live in Tennessee so I guess I will try the 170 jet. Do you guys think this will be OK?
 

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Discussion Starter · #6 ·
Air screw

What about the air screw? 2.5 turn from bottomed? Not sure of the elevation here in tennessee?
 

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QUOTE ("1996yfs200":2zjmfw6w)
remember that temperature and elevation are a huge factor in jetting.
Yea I dont understand jetting at all

The entire elevation/temp thing confuses me. Dos anybody have a link to a website or something that really explains it for you?
 

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The concept is fairly simple. Higher temperatures makes the air less dense (less air in a given volume than with cooler temps). Higher altitude also makes the air less dense (due to the lower atmospheric pressure at higher altitudes). So the hotter and/or closer to sea level requires a larger jet (more fuel) to keep the air/fuel ratio at an optimal mixture. Run the mixture too lean (too small of a jet) you run the risk of burning pistons or valves from a hotter combustion. Run the mixture too rich you run the risk of fouling a plug. Richer is safer than lean, but lean makes more power.
 

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hmf jet

when i got my pipe and jet i told hmf where i ;lived and they sent the proper jet with my pipe
 

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QUOTE ("cwsnake":1d1z6q0z)
The concept is fairly simple. Higher temperatures makes the air less dense (less air in a given volume than with cooler temps). Higher altitude also makes the air less dense (due to the lower atmospheric pressure at higher altitudes). So the hotter and/or closer to sea level requires a larger jet (more fuel) to keep the air/fuel ratio at an optimal mixture. Run the mixture too lean (too small of a jet) you run the risk of burning pistons or valves from a hotter combustion. Run the mixture too rich you run the risk of fouling a plug. Richer is safer than lean, but lean makes more power.

Well 1 how do you know what altitude you are at.
and 2 what happens if you ride in differant locations? Do you have to rejet then?

I am about half way from the coast to the mountains in NC. We ride here everyday so that part would be easy. But our club goes up the the high mountains of WV and sometimes TN all the time. We also ride down east almost at the actual beach.

What do you do in that situation? I mean you are ranging from a few feet above sea level to the mountains where I dont know the elevations
 

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The DynoJet instructions explain everything very well, if you re jet for stock pipe or new pipe and altitude levels, I had no problem figuring it out
 

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If I remember correctly, the jetting is the same from 0 to 3000 ft. One jet size less for over that. It is in the jet kit instructions though. I would think you could find something that works all around. Just check your plug from time to time to see if it is rich or lean. White plug electrode means lean, black means rich. A little lighter than chocolate is good. Do a search on the web there are some pictures of the different conditions out there.
 

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When you take the float chamber, "bowl" off the bottom of the carb to change the main jet do you have to watch out for any pieces to fall out? Is the main jet right there or do you have to take anything else off to get to it? Like the float or anything else have to come off to get to the jet.
 

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QUOTE ("cwsnake":31s9e95d)
If I remember correctly, the jetting is the same from 0 to 3000 ft. One jet size less for over that. It is in the jet kit instructions though. I would think you could find something that works all around. Just check your plug from time to time to see if it is rich or lean. White plug electrode means lean, black means rich. A little lighter than chocolate is good. Do a search on the web there are some pictures of the different conditions out there.

Ok so from sea level to 3000 is the same jet.

But what would you do in this situation. I just got the elevations of some places we ride.

1. my home 860ft
2.Hilltop WV 3410ft
3. FG one county over 2650
4. Most of the NC mountains are in the 3000 mark
5 with the exception of some of the southern mountains where some good trails are that are close to the 5000 mark if not over in some places.


I wouldnt know where to start jetting. I could jet for my home (under 3000) but that jetting would be off in some of those locations. and in some locations bad off. see what Im saying?
 

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Like I said, your best bet is to jet following the instructions for your majority type of riding. If you jet it a little rich while at high altitudes, you should be OK at lower altitudes. It is not a fine adjustment anyway. You will need to inspect the plug at both high and low locations to see how rich/lean you are. All quads are a little different, you will have to tune yours to your specific setup (pipe,filter,snorkel, etc.). Just mess around with it and check your plug. If it is white, increase the jet size. You wont mess anything up by running rich (black plug) except for maybe fouling a plug.

Bexxter, when you take the bowl off, pay attention to the plastic shroud that is around the jet. It only fits right one way so shouldn't be too big of a deal if it falls out when you take the bowl off. Turn the carb a far upside down as you can. The jet is right there in the middle. Download the instructions from DYNOJET and there are pictures.
 

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Discussion Starter · #17 ·
Jetting

Well got my Dynojet kit in and I am now waiting on my HMF, I ran it with stock exhaust after the jet kit install and didnt really notice anything as far as improvement but the stock pipe was holding it back im sure, I did notice another 1 or 2 mph gain wide open though.
 

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Jet kits

I'm wondering where is the best place to but the Jet kits. I 'am planning on leaving my stock pipe on. Is it going to be worth it to leave the stock pipe with the kit. Thanks for any help.
 
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