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post #1 of (permalink) Old 05-28-2001, 12:00 PM
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jetting my overheating quad

I took my current project quad out for a test ride two days ago, The work i did on the chasis really came out great, but after a half hour, my bike shut down. I could kick it and have it run if the choke is on, but it stalls if you give it gas or put it into gear. Any way I towed it home, and was able to pop start it along the way. When i got it home it was back fireing and really running like sh***. I was able to get it to run fairly well again, but i want to fix this.
I replaced the plug after it stopped, the old plug's tip is white. This means it is running lean, right? If i remember other people i knew with this bike found that it shuts down if it losses all oil or overheats. So this must be the reason for it shutting down, if anyone has any other guesses or ideas let me know.
When i took the minuki carb apart the needle clip was on its lowest position (richest if I read the manual correct), it has a 115 main (stock is 110). I am going to try a new needle and jet but i am not good at jetting four strokes and am not sure how rich to go. It's an 89 suzuki quadsport 250. The bike has an aftermarket pipe/silencer, It's boared over with larger valves and ported(30 over i was told, but i can't be sure as I did not do the work), there is a 2" wide or so hole drilled in the airbox lid. I was also told The bike was jetted "so it's plug reading is correct" when i bought it. Another facter may be that it was bought in the mountains of penn. and i live at sea level.
Sorry to make this post so long, but i wanted to get all the information into it.

ktmbk
83 ATC 250r (with many extra parts 4 sale), 83 ATC 185s, 89 zuki' 250sport.
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post #2 of (permalink) Old 05-28-2001, 06:45 PM
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Re: jetting my overheating quad

Your definaly lean. I would go up a couple sizes in the mains and get the next richer needle. Fire it up and let it idle for 5 minutes and than check the plug to see if it lean or o.k. You could than ride it 1/4 throttle for a half a mile or so and check the plug again. You can it if for 1/2 and full. It would makes sence if this quad was setup for the mountains since it is way to lean for sea level.

post #3 of (permalink) Old 05-29-2001, 08:37 AM
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Re: jetting my overheating quad

it does sound like you are running lean, i would adjust your jets and make it a little richer. it will probably be a "try and see" type deal, just keep doing the plug tests and make sure to use a new plug on every plug test. hope this helps

Chris [img]/wwwthreads_images/icons/cool.gif[/img]
<font color=blue>You dont quit riding because you get old, you get old because you quit riding!</font color=blue>
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post #4 of (permalink) Old 05-29-2001, 04:44 PM
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Re: jetting my overheating quad

you don't have to use a new plug on each test. just clean it off with a wire brush and wd-40. when you think your plug look o.k than put a new plug in and than check it.

post #5 of (permalink) Old 05-29-2001, 06:17 PM
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Re: jetting my overheating quad

Seems that I will not be able to get another needle for the bike, I can get the one i have, but not a richer one. I have 4 jets on their way. Tomorrow i am going to try a carb specialty store i heard about on the web, but I am probably out of luck. Anyone have any ideas? has anyone used a power jet kit on their bikes? if so how do they work and will it help my problem? thanks

ktmbk
83 ATC 250r (with many extra parts 4 sale), 83 ATC 185s, 89 zuki' 250sport.
post #6 of (permalink) Old 05-29-2001, 10:18 PM
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Re: jetting my overheating quad

when you get a power jet kit from DYNOJET they come with new metering rods, and about 6 differant jets

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post #7 of (permalink) Old 05-29-2001, 10:50 PM
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Re: jetting my overheating quad

to get the most accurate reading, it is best to use a new plug on every test. i am not saying to throw the plug away after the test and never use it again, just put it back and use a new one for the next test. i have tried this both ways and its much more accurate to use a new plug...and alot quicker too.

Chris [img]/wwwthreads_images/icons/cool.gif[/img]
<font color=blue>You dont quit riding because you get old, you get old because you quit riding!</font color=blue>
post #8 of (permalink) Old 05-30-2001, 10:56 AM
 
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Re: jetting my overheating quad

You didn't mention at what throttle position you were running to produce the white plug reading. That should give you an idea which area of the carb to look at. Eg: pilot jet, pilot air screw, needle jet or jet needle, main jet. Also make sure the float level is set to spec. This could give you a lean condition across the board if float level is set too low. Also this is a four stroke engine and as such it is really hard to get spark plug readings because there is no oil mix like a 2 stroke has. What kind of altitude had it been set up for? Assuming it was right for where it was set originally you should be able to use a mikuni slide rule to figure out the new jetting. For example if the altitude was 4000 feet then the new jetting for sea level would be 122.5

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post #9 of (permalink) Old 05-30-2001, 05:28 PM
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Re: jetting my overheating quad

What kind of carb do you have. You can go to the website for keithin www.keihin-us.com/ and www55.mikuni.com/index_mac.html
they should have everything you need for jetting since they make the carbs

post #10 of (permalink) Old 05-30-2001, 11:23 PM
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Re: jetting my overheating quad

The throttle position was varied, as I was just riding normal when the bike shut down, and not looking for a plug reading, if i had to choose a position it would be in the 1/2 to 3/4 range when the bike stopped and i pulled the plug. As far as altitude, all i can say is that it is set up for the montains, as i bought it two states over, the guy who sold it to me didn't know, but he said that the carb was jetted perfect to the plug for where he was. I did change the plug when i brought the bike home so it only was used for the one ride, so the reading would be true for ride-ing around here. I don't have a mikuni measure slide, but i now have the following jets 117.5, 120 ,122.5, 125. (there is a 115 in there now, these were the next four sizes up). Getting a needle is out at this time, as even the suzuki dealer does not seem to know how to convert their "mikuni #'s" to the standard mikuni numbers in the catalog. hopefully i can compansate for the needle with the main, i am not sure how effective it is going to be as every chart listing which carb piece affects where in the jetting is different an example is one says the main starts to pick up where the pilot ends, another says that the main only affects the wide open throttlejettint with the needle affecting everything in the middle. for now I am going to check out that sight curtisschults listed, see if i can learn more about jetting four strokes,tomorrow i will play with the main to see if i can get anywhere. thanks guys for all your help so far.

ktmbk
83 ATC 250r (with many extra parts 4 sale), 83 ATC 185s, 89 zuki' 250sport.
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