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Discussion Starter #1
I should have never read the "How Fast Can you go thread". I figured if ya'all can do it I can to.

57 miles an hour was the last time I looked at the speedomoter. I was too busy keeping the Grizzly on the road. When I backed off the throttle for a corner the Grizzly backfired. (I am quite sure it was the Grizzly and not me, But...I was a little nervous at that point.)

When I got home I had to do a little mainterance on my Grizz. I had to iron the seat for an hour to get the pucker marks out.

I am worried about the backfire. I am afraid that it might blow the packing out of my exhaust. Was the backire caused by the build-up gases, or do I have some other problem? Is this something that I should worry about? Does it happen to all of you go fast "Grizzly Hearders" out there?

I was riding the San Rafael Swell at about 6500 ft elevation. I have had my carberator jetted for the higher altitude. The only time I have ever had the Grizz backfire is when I was playing "GO FAST GAMES". Other than that the Grizzly seems to run great.

The picture is of the Eagle Canyon Arch in the San Rafael Swell. (I am innocent..I did not go very fast in the swell- honest officer!!!)

Any suggestions on the backfire problem?
 

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i think what you may have experianced is what has been endearingly coined the Grizzly Fart,,,not to be confused with the Hoo Phart,,,,although even though ive never experianced the Grizz fart,im told its more of a poof type fart,not the blow a hole in your shorts,clear a room type of fart

if anything if your jetted for a higher elevation than for where you normally ride you would be running lean so i dont think you would be loading up with gas unless your float is sticking when your throttling at higher speeds,and not adjusting fast enough when you let off

if your jetted for a higher elevation,your jet size went DOWN to compensate for the thinner air (less oxegen)

valves may need to be adjusted,,,,you might want to pull the carb,and put the right jet back in for your elevation,and while your in there spray the carb out real good with some good carb cleaner

what year Grizz?last time valves were adjusted?
 

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oh yea,,,,the had to iron the seat remark,,,,,loved it,cracked me up
 

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I've had the poof type fart. It used to happen when it was brand new last winter. I'd shut the bike off and you'd hear the poof.

When I went riding down in WV, I had to poofs but much louder backfiring. Kind of like the farts you have when you first wake up. But it's nothing to worry about. Theres so many factors that come into play like altitude changes etc. I also read that if you are on the throttle on an uphill. Putting a good load on the engine and then let off you can get that backfire. This is exactly how mine happened.
 

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Mine backfires more when valves need to be adjusted but I get the occasional backfire everytime I ride...never stopped to really think about the cause...I hope there's nothing wrong w/ the bike
 

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mine never backfired until i put the Dynojet kit in. more of a poof backfire after shutting it off. and the other night when i went out in the dark, the grizz sat there idling for a couple minutes and i noticed the head pipe was nicely glowing a bright orange color. would a little richening of the pilot screw fix this?
 

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WOW... thats hot. I dont think anything on my quad glowed... but I never really checked either. At any rate, that sounds like it is way to hot to me.

Jim
 

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Mine does it when I run it wide open for a minute or so and let off the throttle.
 

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sounds like your burning lean,,,more oxegen added to the air fuel mixture equals hotter ignition

whats your plug look like,,,thats a real good way to burn your valves if thats whats going on (running too lean),,,,all of that heat has to pass through your exaust valves to get to your exaust in order to get it glowing like that,,,also if thats whats going on,it can burn a hole in your piston
 

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i have never seen mine glow,and ive rode the dog crap out of mine in some pretty hot weather
 

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I think a small backfire when you shut it off is normal. It usually depends on where it is in the cycle when it shuts off. At idle I think the engine cycles about 1 1/2 times after you shut the key off which means you have a shot of raw fuel in the motor. If the motor is hot it will ignite it and you get a pop.
As far as backfiring when you let off the throttle, I think that is an indication that you are a little lean but I don't know for sure. Have you done any modifications or are you just stock. Stock machines usually run a little rich.
 

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Starky,adicted2mud said his header pipe gets glowing orange,,,has yours ever gotton that hot?
 

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I believe a plug chop is very much needed here to figure out how you are running. One would think it is running very lean. Although I have never really paid particular attention to my header pipe I have looked into the engine enough times while it is hot that I should have noticed a glowing pipe if there was one. Please tell us any and all modifications that have been done to your machine and did you buy it new or was it previously owned by someone?
 

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Discussion Starter #14
Thanks for all of your posts. I probably have what HooPharted described as a "Grizzly Fart".

This is the real value of this forum. If there is a problem with your machine it is nice to know that you are not the only one.

I don't mind my Grizzly farting if everyone else's is farting also.
 

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so it's time to fess up. when i bought the grizz new it was running way rich, to the point if you ever let off the throttle in the mud or going up a hill it would start to miss and bog down when you got back onto the throttle. so i was going to put a jet kit into it, but that got backordered a couple of times so i put a pipe on and drilled some uni vents into the airbox to lean it out. FIXED the problem completely and run good with no header glowing and no Grizzly farts. now the Dynojet kit finally shows and i install according to instructions for the pipe and the elevation.(instructions don't have provisions for air filter of air box mods) take it out for a ride, lost my bottom end catwalking power and farting every time i shut it off. so without checking the plug i assume runnimg rich and drop 2 sizes in main jet and screw in mixture screw to 1.5 turns off seatting instead of 2.5 as instrucions had me do. now i notice the header getting hot at idle and when i'm just barely putting around. the pipe cools down as soon as i open it up to 1/3 or more throttle as far as i can tell. NOTE when the headers hot the engine isn't hot-fan hasn't kicked in yet.
 

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whats the plug look like since you noticed the glowing header,,,,you should go back to 2.5 turns on the mixture screw,,,,,4th clip on the needle (if its a dyno jet,i dont know about others),and i ended up with a 175 Main jet with my mods,,,which sounds alot like what your going to end up with

im still running a tad rich with this carb setup i mentioned,,,just a tad though,and am thinking of getting the Dial a Jet setup to get it fine tuned just right,,,,its just such a pain to pull all of that apart each time you need to make a little adjustment,i think one last time to install the DaJ would be soooo much less ainless,lol

i cant stress enough how much safer for your motor it is to be on the rich side,and bring it in to where you need to be,,,,rather than too lean,and bringing it up

my suggestion to you is to go to these settings i mentioned that are close,,,,go buy about 6 plugs (not like you wont ever use them,and there cheap),and put a fresh plug in,run for awhile,pull the plug,make any adjustments if needed,,,fresh plug,and repeat until you are where you want to be

i have no back firing,plenty of top end,exceleration,low end torque,no stalling,and hill climbing ability is fine with this setup,its that close,its just the plug isnt burning like i want it to
 

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hey Hoo, looking at my dynojet kit and the jets don't go anywhere near 175's my biggest in the box is a 160. i do realize dynojet numbers don't match other brand jets of the exact size, so are you running dynojet 175 or another brand of separetely purchased jet? i was supposed to install dj150's for my altitude (3700') with a high flow pipe, but now i put in a dj148. What's your altitude? -----i see your running a dubach pipe, how do you like it?
 

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no your right,,,you will have to get on the Dyno Jet web site,and order it,,,,they are real cheap,i think they were like a buck a piece,,,so since your going to order one,you might as well order a couple differant sizes,like the 175,and a couple below it,,,,theres nothing saying your bike is going to react exactly like mine,but the 175 is your best starting point,but if you have to you will atleast have one or two below the 175 that doesnt come with the kit

the kits jets cover basic mod ranges,,,by drilling the air box,and installing the Uni Vents,you are getting a much greater volume of air than what the kit was intended for,,,however the needle in the kit is nice,i think it has 5 positions where the stock i think 2,or maybe it was 3,,,and it also gave you the new springs and such

i have 10 vents in my lid
 

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When you switched to the Dyno Jets did you change to a Dyno Jet needle. You can't use the stock needle with the Dyno Jets.
I've never noticed my header glowing but my Griz was still stock when I was riding it, so it would have been running rich and you shouldn't get a glowing pipe if it's rich. My Raptor and YZ250F would glow bright red when I let it idle for any time at all but both of those were set spot on for fuel/air mixture.
Because you have a lot of idle time on these machines you want them to be a hair on the rich side so they don't cook themselves.
 

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Ok, so i let it idle for a while today and pulled the plug, it was a lite tan color-spot on i'd say but i'm not willing to put up with the glowing headers. So i reset the mix screw to 2.5 turns off seat. Did another idle time and plug test, now plugs black as coal so i set screw to 2 turns off seat and tested again. This time spark plugs black with tan edges and no glowing. I'll try this bottom end setting for a little while. Now to fine tune the higher rpm range. Starky i am using the dynojet needle also.
 
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