1995 xr100 jetting help

[ccman60]

Just bought a abused 95 xr100 that wasn't running, but came with a new complete fmf pipe set up. The carb was varnished up so I bought a chinese Runtong carb that was brand new and tried to get it going. It's hard to start and won't idle. What should be the base start for the air mixture screw? 1 1/2 turns? I am in the process of cleaning the original carb, and I am guessing I will need new jets. Could someone please give me some advise as what size jets with this FMF setup might work? I am at roughly 500ft. above sea level, and the needle clip is in the 3rd slot from the top. Any advice would b great. Thanks, Chris.

[ccman60]

I now have the bike running with the new chinese carb, with whatever stock jetting is for their set up on a xr100. ( no #'s on the jets ). The bike starts on the 1st or 2nd kick idles fine, comes off the choke once warmed up and idles fine, but if you give it a hand full of throttle it will bog and die if you don't release the throttle. Can someone give me some advice on where the clip should be set on the needle? It is currently set at the # 3 setting of 5. ( middle ). Also I have the air fuel mixture screw ( bottom of carb- not the side one ) at 2 turns out. Thanks for any help, Chris.

[wakiki]

just try tinkering, theres no real "trick" to jetting and tuning... just try different settings and see how she runs, look at the sparkplug and adjust accordingly. pilot and both screws for idle, needle for mid throttle, and main jet for W.O.T

I just finished a 1990 xr100 with a 132 bore kit, cam, bigger intake, 30mm carb, and some porting done and spent quite a few days tuning the carb, but don't get discouraged, if at first you dont suceed....

[jkjet]

I have a 96 xr 100 with a 115 kit, stock carb, UNI filter, after market exhaust. I just added the exhaust ( my buddy gave it to me to mess around with) and I had the same bog. I dropped the needle clip position form three (middle) to 1 (bottom). The theory being that it needed more fuel. It runs great now, but I feel like it should have more punch. I'm going to up the main jet as soon as I figure out what is in there. Bike Bandit lists #90 and #95 as possible main jet sizes.

[wakiki]

i believe stock xr100 runs a 95 main and a 38 pilot i believe... You can buy a jet kit for around 15$ from tbparts.com just change em around and run it around the block to see how it feels

[Racer]

Just bought a abused 95 xr100 that wasn't running, but came with a new complete fmf pipe set up. The carb was varnished up so I bought a chinese Runtong carb that was brand new and tried to get it going. It's hard to start and won't idle. What should be the base start for the air mixture screw? 1 1/2 turns? I am in the process of cleaning the original carb, and I am guessing I will need new jets. Could someone please give me some advise as what size jets with this FMF setup might work? I am at roughly 500ft. above sea level, and the needle clip is in the 3rd slot from the top. Any advice would b great. Thanks, Chris.

Pretty much impossible to tell you what jetting with that China carb, you may be able use the stock jetting from the factory carb but you'll have to swap out the needle and throttle slide too. Generally the china carbs use smaller main jets than stock and a richer [fatter needle] and shorter throttle slide but not always.

[jkjet]

I have a 96 xr 100 with a 115 kit, stock carb, UNI filter, after market exhaust. I just added the exhaust ( my buddy gave it to me to mess around with) and I had the same bog. I dropped the needle clip position form three (middle) to 1 (bottom). The theory being that it needed more fuel. It runs great now, but I feel like it should have more punch. I'm going to up the main jet as soon as I figure out what is in there. Bike Bandit lists #90 and #95 as possible main jet sizes.

I pulled the stock main jet out of my 96 xr and it was a #95. I was able to aquire a #98 out of a 2004 model and it runs better at full throttle. I may try to up a bit more.

[ccman60]

I went to our local Honda Dealer and ordered a 105 main and a 40 pilot, should be in this friday. In the mean time I will re-clean the carb and see if that helps.

[ccman60]

Took the stock jets out of the OEM carb and put them in the chinese carb to see if that would make any difference and it didn't. The bike will rev ( though a little rough ) with the choke on, once the choke is off the bike will only rev to 1/4 throttle or so, twist the throttle any farther and it dies. I am going to go back out to the shop and move the needle to the bottom setting and see if that helps. Friday the new jets will be in, but I can't imagine new jets clearing up this problem. Any advice would be great, as always, THANKS, Chris.

[Racer]

Took the stock jets out of the OEM carb and put them in the chinese carb to see if that would make any difference and it didn't. The bike will rev ( though a little rough ) with the choke on, once the choke is off the bike will only rev to 1/4 throttle or so, twist the throttle any farther and it dies. I am going to go back out to the shop and move the needle to the bottom setting and see if that helps. Friday the new jets will be in, but I can't imagine new jets clearing up this problem. Any advice would be great, as always, THANKS, Chris.

As I said before, most chinese carbs use a different throttle slide and needle and switching jets won't help. You have to swap out the needle and slide too. Otherwise put the stock chinese jets back in and dial it in from there.

Next check the valve clearances and adjust to stock specs. Then make sure the air filter is clean and pop in a new spark plug. Wouldn't hurt to change the oil too.

[ccman60]

Well I moved the needle clip to the very bottom position to the the very top and no change from 1/3 throttle on. I took the bike off the stand and with the needle clip at the top (lean ? ) I took it for a ride. Starts on the first kick, idles great and takes off great, but give much more than 1/3 to 1/2 throttle and the bike will bog and die if you don't back off the throttle. I noticed cracks in the rubber intake so while idling I sprayed some starting fluid on the cracks and it dropped the RPM's and killed the motor. Fired right back up, could this be the problem???? Thanks, Chris.

[Racer]

As I said before, most chinese carbs use a different throttle slide and needle and switching jets won't help as it will then be too rich. You have to swap out the needle and slide too. Otherwise put the stock chinese jets back in and dial it in from there.

Next check the valve clearances and adjust to stock specs. Then make sure the air filter is clean and pop in a new spark plug. Wouldn't hurt to change the oil too.

[Racer]

Well I moved the needle clip to the very bottom position to the the very top and no change from 1/3 throttle on. I took the bike off the stand and with the needle clip at the top (lean ? ) I took it for a ride. Starts on the first kick, idles great and takes off great, but give much more than 1/3 to 1/2 throttle and the bike will bog and die if you don't back off the throttle. I noticed cracks in the rubber intake so while idling I sprayed some starting fluid on the cracks and it dropped the RPM's and killed the motor. Fired right back up, could this be the problem???? Thanks, Chris.

Generally cracks on the intake don't go all the way through and if they do, will result in a "hanging rpm" and the engine will rev higher if you spray WD40 around the cracks.

[Racer]

After you finish checking the valve clearnaces and air filter, take out the throttle slide and compare it to the one in the stock carb. If the slide is shorter on the Chinese carb, replace it and the needle with the one from the stock carb.

[ccman60]

Thanks for the advice Racer, Air filter is clean, will swap out china needle and slide with original and see if that helps. Should also pick up new jets today.