Let's talk RMX's
-
bufftester
- Platinum Member
- Posts: 3461
- Joined: 06:03 pm Oct 31 2012
- Country: USA
- Location: University Place, WA
Re: Let's talk RMX's
Finally got the carb gasket swapped out which fixed my fuel leak. Now I'm down to 2 issues that are holding me up. First is just getting the bike started. Put a new plug in and opened the petcock. With full choke and no throttle gave it a kick and it fired up then died after a couple seconds. I know the fuel is flowing to the carb. After that initial start tried kicking for a bit and nothing. Pulled the plug and its wet. New plug in, first kick fires up, runs a few seconds then dies. Did that 3 times (it was all the new plugs I had lol). Not sure if it's a carb issue not flowing fuel, pulling it tomorrow to reclean it and check. Other thought was possibly a coil or CDI spark problem. Appears to have spark (using the old plug against the head check) but isn't a nice big fat spark like I was expecting. COmpression is 150 and leakdown check was good, reeds are new and fresh pack on the silencer/new air filter. Any ideas? The second issue I am having is the rear wheel. The PO put a 19" rear wheel on it, but not sure what year it came from. With the proper wheel spacers for the RMX hub the brake disc is aligned perfectly with the caliper, but there is a .5" gap between the left side spacer and the inside of the swing arm. I cut down a second spacer to fit the gap, but must have made it a bit too long as now the rear wheel feels like it's binding. Tried finding an RMX rear hub on Ebay, but they aren't cheap. If I can get this one sorted I'll stick with the 19" rim for now.
-
Jaguar
- Supporting Member
- Posts: 590
- Joined: 01:32 am Jul 03 2013
- Country: Paraguay
- Location: Paraguay
- Contact:
Re: Let's talk RMX's
plug in/out all connectors for the ignition system in case they have some rust. If that don't help then find a long downhill you can use to push start the bike. Gong downhill will keep it running so you can get a better idea of what is wrong with it. If it dies immediately while running then that points to an ignition problem. Jetting problems are not so on/off. A weak ignition system needs revs to keep the spark healthy.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
-
kawagumby
- Gold Member
- Posts: 927
- Joined: 10:09 am Nov 30 2006
- Country:
- Location: California
Let's talk RMX's
Finally got the carb gasket swapped out which fixed my fuel leak. Now I'm down to 2 issues that are holding me up. First is just getting the bike started. Put a new plug in and opened the petcock. With full choke and no throttle gave it a kick and it fired up then died after a couple seconds. I know the fuel is flowing to the carb. After that initial start tried kicking for a bit and nothing. Pulled the plug and its wet. New plug in, first kick fires up, runs a few seconds then dies. Did that 3 times (it was all the new plugs I had lol). Not sure if it's a carb issue not flowing fuel, pulling it tomorrow to reclean it and check.
Were all three wet after it fires up? If so, you probably have fuel/0il built up in the crankcase that causes the foul. Pull the plug, crank over a bunch of times to clear, see if it runs any longer before it fouls after that. If it does, you just need to repeat that operation until it clears. (A lot of work, LOL, ask me how I know). The case induction means that it is a lot easier to fill the case if the carb leaks. Could be old fuel that's been sitting too.
Other thought was possibly a coil or CDI spark problem. Appears to have spark (using the old plug against the head check) but isn't a nice big fat spark like I was expecting.
Mine doesn't throw a big fat spark either.
The PO put a 19" rear wheel on it, but not sure what year it came from. With the proper wheel spacers for the RMX hub the brake disc is aligned perfectly with the caliper, but there is a .5" gap between the left side spacer and the inside of the swing arm. I cut down a second spacer to fit the gap, but must have made it a bit too long as now the rear wheel feels like it's binding. Tried finding an RMX rear hub on Ebay, but they aren't cheap. If I can get this one sorted I'll stick with the 19" rim for now.
I use a 19" on my 87 kdx and it works fine for trail riding, IMO. I used to race KX250's off-road with 19" rims, and I could never tell enough difference between the two to warrant the effort to convert. But I'm no purist....
I just put a PWK 39 on mine (used from ebay) and a huge difference in response and proper fuel-mixture. My bike had the mikuni 38 and I could not get it to work well no matter how I jetted it - it was OK on the trail, but on the street it was inconsistent - seemingly affected by temperature and whimsey. The Keihin was better from the first kick start (a first) to cruising at 55 MPH on the road. I'm very pleased. I'll get it on the trail next week, but I'm liking what I've seen so far.
Were all three wet after it fires up? If so, you probably have fuel/0il built up in the crankcase that causes the foul. Pull the plug, crank over a bunch of times to clear, see if it runs any longer before it fouls after that. If it does, you just need to repeat that operation until it clears. (A lot of work, LOL, ask me how I know). The case induction means that it is a lot easier to fill the case if the carb leaks. Could be old fuel that's been sitting too.
Other thought was possibly a coil or CDI spark problem. Appears to have spark (using the old plug against the head check) but isn't a nice big fat spark like I was expecting.
Mine doesn't throw a big fat spark either.
The PO put a 19" rear wheel on it, but not sure what year it came from. With the proper wheel spacers for the RMX hub the brake disc is aligned perfectly with the caliper, but there is a .5" gap between the left side spacer and the inside of the swing arm. I cut down a second spacer to fit the gap, but must have made it a bit too long as now the rear wheel feels like it's binding. Tried finding an RMX rear hub on Ebay, but they aren't cheap. If I can get this one sorted I'll stick with the 19" rim for now.
I use a 19" on my 87 kdx and it works fine for trail riding, IMO. I used to race KX250's off-road with 19" rims, and I could never tell enough difference between the two to warrant the effort to convert. But I'm no purist....
I just put a PWK 39 on mine (used from ebay) and a huge difference in response and proper fuel-mixture. My bike had the mikuni 38 and I could not get it to work well no matter how I jetted it - it was OK on the trail, but on the street it was inconsistent - seemingly affected by temperature and whimsey. The Keihin was better from the first kick start (a first) to cruising at 55 MPH on the road. I'm very pleased. I'll get it on the trail next week, but I'm liking what I've seen so far.
1994 KDX200, Beta 200rr, yz125, yz250, kx100 modded for adult, gasgas contact 250.
-
bufftester
- Platinum Member
- Posts: 3461
- Joined: 06:03 pm Oct 31 2012
- Country: USA
- Location: University Place, WA
Re: Let's talk RMX's
I have read that the PWK39 is the way to go on these. Will try clearing the case out with the plug removed. Checked the spark gap with a tester and it seems good, so maybe its just a fuel issue. I don't have a problem staying with staying with the 19" wheel other than right now it is just binding. Hope to get to it this weekend and try to work it out.
-
kawagumby
- Gold Member
- Posts: 927
- Joined: 10:09 am Nov 30 2006
- Country:
- Location: California
Re: Let's talk RMX's
on another thread you said; "On a different note, I am having starting issues on my RMX. Starts after a couple kicks cold, runs a few seconds and dies. Won't start after that. Pull the plug and it's wet. Dry it off, kick the bike over a few times, put it in and it fires for a few seconds and the same thing...over and over...very frustrated with it right now."
It sure sounds like there is fuel leaking into the case. Mebbe a leaking fuel valve and a too high float level or leaking needle valve? I had a heck of a time getting mine to run after a leaky needle. It took nearly an hour of cleaning the plug, run for a short while, kick it over a bunch, and start the cycle over again. The case induction just makes it that much more an issue.
It sure sounds like there is fuel leaking into the case. Mebbe a leaking fuel valve and a too high float level or leaking needle valve? I had a heck of a time getting mine to run after a leaky needle. It took nearly an hour of cleaning the plug, run for a short while, kick it over a bunch, and start the cycle over again. The case induction just makes it that much more an issue.
1994 KDX200, Beta 200rr, yz125, yz250, kx100 modded for adult, gasgas contact 250.
-
bufftester
- Platinum Member
- Posts: 3461
- Joined: 06:03 pm Oct 31 2012
- Country: USA
- Location: University Place, WA
Re: Let's talk RMX's
Yeah, I am beginning to think that my problem is in the carb. Plan is to find a PWK39 and swap that in. I have verified all the electrical connections and grounds and they ohm out good, so fairly certain its not an electronics issue. Pulled the flywheel and everything there checked good as well. Unfortunately have just been working on it in spurts due to family commitments.