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Discussion Starter #1
I've been running rich for quite some time, and I'm trying to get my carb tuned in good. I bought a new zoom zoom performance carb, and I did feel a difference over my old stock one, but it seems to be running too rich in fuel, as my stock one did. Spark plugs are black, and sometimes wet with fuel. I've been trying to add more air, but I got mixed up with the whole rich or lean, and thought that adding bigger jets would add more air, but just found out it does the opposite. Stock main jet for 450 is 131.5, and the carburetor I just bought came with a 145 main jet in there. My HFM exhaust came with a jet kit with 135, 137.5, and a 140. Stock pilot jet is a 17.5, and I just put in a 22.5 thinking it would lean it out a bit.


My idle seems to go up and down with a sputter, and when I let off the gas the rpm's will go lower than the idle, almost sounding like it is going to cut out. Also, my rpm's seem to get pretty high once I hit 3/4 throttle (main jet) and I'm hitting my rev limiter at around 48 miles an hour. I do have cvt mods including 18G OD weights and Orange secondary with stock belt... Is it possible that I'm running too big of a main jet? and too big of a pilot jet? I never got around to adjusting the needle yet, which I'm thinking I might have to to get to lean out.


Anyone have some experience jetting a 450 grizz with aftermarket exhaust? specifically HMF performance if possible? Would like to know what you did to lean out your fourwheeler, and what was the best settings you've found with your carburetor? It would be nice to have a good idea what a 450 might require, and get a good starting point or target. Thanks.
 

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Discussion Starter #2
I just put in the stock size 17.5 pilot jet (1.5 turns out) and put in a 135 main jet (one step up from 131.5 main) and my fourwheeler is running alot better. I was able to hit 51 mph without hitting any rev limit. So the main jet was way too big and I was running way too rich. So I think I'm heading in the right direction. I think the main jet is good, but I'm not entirely sure if I need to go up in pilot jet, and I then adjust the needle (which I haven't messed with at all yet). I'm letting the fourwheeler cool off before pulling the spark plug to see how it's running now.


If anyone has experience jetting their 450 grizz or kodiak with an HMF Exhaust with or/without EHS lid. I'm waiting on my lid, and I know I will likely have to rejet again, or if I'm lucky it will lean it out with the setup I got now to a better ratio.
 

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I had 2 2007 griz 450's and had jet kits in both. Let me tell you, it's a frustrating thing trying to jet these ATV's. I had a pipe on one of them. Not and hmf. Its really not worth the time if you ask me. If you get it right , leave it alone and don't try to squeeze out any more, it's a waste of time. Put a machined sleeve on it and shim it . Your not going to make that much a difference in throttle response or noticeable power gains with the carb. I finally sold both and bought a 2017 grizz700 se . I loved my 2 450's and tricked them out as much as possible without big bore job. The only thing I didn't do that might have added a bit was a piston job( without bore)
 

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I had 2 2007 griz 450's and had jet kits in both. Let me tell you, it's a frustrating thing trying to jet these ATV's. I had a pipe on one of them. Not and hmf. Its really not worth the time if you ask me. If you get it right , leave it alone and don't try to squeeze out any more, it's a waste of time. Put a machined sleeve on it and shim it . Your not going to make that much a difference in throttle response or noticeable power gains with the carb. I finally sold both and bought a 2017 grizz700 se . I loved my 2 450's and tricked them out as much as possible without big bore job. The only thing I didn't do that might have added a bit was a piston job( without bore)



Well my new carb did make a difference on throttle response... guessing it has a modified spring in it. Today I made some progress, and I feel like I'm heading in the right direction now. It's running alot better than before. I just need to wait for my EHS airbox lid before I can really fine tune it. Once I get that tuned in I do plan on putting in a 1mm shim again. As for the machine sheave, that will be a future purchase when I can save up enough money... JBS is making a new "extreme sheave" and is supposed to be better than their original jbs sheaves, and is currently in testing. I'm hoping that will make a good difference as well. I am looking in to a few more things for future performance upgrades too. thunder products dial-a-jet kit I heard works pretty well, mainly for saving trouble having to change out jets all the time. I was also checking out those "torque wings" they make... expensive but sounds promising. I'm gonna keep giving it love. It's a beast, it's just running rich... running leaner today, but needs a bit more of a adjustment. But I do feel like I am heading in the right direction to getting it tuned in finally...
 

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I had the ehs lid and thunder product jet setup on one and a Dynojet kit in the other. IMO the thunder jet worked better. It's pricey though. I ride in RI and go to NH twice a year and it's a big change in elevation and the thunder can be adjusted on the fly. I couldn't wait to upgrade to a bigger Atv with no carb.
 
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