RMX hard starting

[CyberChrist]

I just purchased a new to me 93 RMX 250. I'm having a heck of time getting it started. Compression is 140psi cold, and 180psi cold with a squirt of two stroke oil in the cylinder. I can eventually get it started with about 1/3rd throttle and chock after about 20 kicks where it's fully loaded. Spark is good, compression (near as I can tell) is good, air filter is good, and once it's started it runs like an ape it's just so damned difficult to start. I do the normal tricks of lean it over on the left side for 3-4 seconds and all, but my friends RMXs kick over with just 1-2 kicks. It's got a bore on it, and the folks I bought it from called it a 320 kit. Near as I can tell that's like 9mm over so it's gotta have a steel sleive. I've gone through the carb and it looks OK to me. I can't believe it's been this much of a bear it's whole live since the bore in 94 (I've got receipts from Klemm Research for the work in 94) so it's gotta be something. I'm just about out of ideas. One friend said it's probably the porting, dunno. Anyone???

 

[placelast]

I have two RMXes; neither are difficult to start but do get that way when it's time for a top end or if the jetting is (way) off.

Eric Gorr has a 300cc barrel for sale. I thought about buying it for mine, but he forewarned me that it requires perfect fuel, and the standard bore is much easier to work with. Therefore I decided against it.

So perhaps your's needs good, fresh fuel and some tinkering with the jetting, in particular the starting circuit.

Does it have the stock PJ carb? That's not the best one in the world. The manual might help in troubleshooting the carb's starting circuit(s) woes.

Klemm is still in business although it may be under a different owner at the moment than the one who did the overbore for yours. The store is in Riverside, CA, if that helps.

 

[CyberChrist]

Thanks for the feedback. I'm going to go through the carbs again tomorrow. The manual has some jetting 101 stuff (wow, temp effects jetting, go figgure! What a help... Not!) for complete newbies. I'm gonna take a hard look at the slow jet and air screw and make sure everything is snuff there (yet again) but with pulling 140psi cold compression and 180 with a squirt of two stroke oil I wasn't worried about the top end. Then again, I dunno what this kit SHOULD pull really. I race a MC18 NSR, jetting strokers isn't new to me, but this one is proving to be a PITA. Thus why I'm now grasping at straws and asking for help. I'll mix up some fresh fuel tomorrow and see how that does... it is running the fuel that came in the bike but the owners were selling it because it was hard to start as well and they owned it for 4 months before I bought it from them. They were upgrading to a YZ426 with the magic button. Wimps! ;)

 

[CyberChrist]

Forgot the other bits, yeah it's still the stock PJ carb. Dunno about upgrading just yet. Don't wanna tinker too much and am also still stongly considering getting a complete new topend and going back to stock bore. I'm gonna take her riding this weekend and see how it goes and see if I can diagnose this starting issue still. If I blow a full week on this and still no dice, then it'll be time for a stock barrel I think. I did a search for Kelmm in riverside and found this:
KLEMM CYCLE SUPPLY
3636 VAN BUREN BLVD RIVERSIDE, CA 92503-4288
(909) 687-0673
»Motorcycles, Etc-Accessories

So maybe that's them these days. Can't hurt for me to call and see. At least they might have records on what porting was done on the beast so I can rule that out or not.

 

[placelast]

I firmly believe it's not the porting, nor top-end condition, but rather the fuel quality, supply volume/ratio-to-air (lack of sufficient fuel vapor of the proper density for starting); that's why my 'smokers are slightly harder to light when the weather changes and I forget to swap jets.

What part of the country are you in?

Does it start better once warm or no?

How does the big bore compare to you buds? Grunty/meaty?

 

[placelast]

Did Klemm do away with the exhaust valve (like the LA Sleeve CR 330cc overbore)?

In a week or so I'll have a line on a stock, good condition OEM '90 RMX barrel + PC/Answer exhaust system, but the former does not have an exhaust valve ($ - ouch). FYI, the '93-up has a different, smaller exhaust port than the '89-'92 which is why you'd need to change things out as a complete system (barrel + exhaust).

As long as pistons are still available for the Klemm barrel then I'd be game for a straight-across trade, part-for-part (not because there's much to gain for me but rather I like the challenge of an experiment).

 

[CyberChrist]

I'm in Seattle, WA. I've had the bike a total of 3 days now. Spent the first two chasing my tail on carb and trying to figure out how to get it to light at all. It's mostly a high HP motor right now. I'll have a better assesment after this weekend after a full day of trail riding and I'll be able to adaquatly compare to stockers I've ridden. I'll say this... it's got some HP to it for sure. Once warm it starts on the first full kick no problem, but again, requires some throttle. Starting with no throttle as all other RMXs I've ridden has gotten me nowhere. I talked to our local expert on such matters and he said it's probably carb. He said the top end is probably just fine with pulling that compression of 180psi. The big bore has more everywhere, and that's part of the problem... I wanted a more sedate trails bike. I don't do air, much less big air. I rotate counter clockwise and land on anything other than the wheels... {shrug} I believe the exhaust valve is indeed still there as it picks up more HP just like my racer when the valves snap, but I've not pulled the cover and looked yet. The top end comes off after this weekend and I'll know a lot more like what the barrel is and how things look in there as I don't have a scope. it's also got a slightly dented FMF Gold pipe on it now, and that contributes to the excessive HP as well I'm sure. Reeds are in great condition. I'll be looking to tune for much more torque, and my wrench says that it's absolutly possible with some tweaking probably with this barrel, but we won't know for certain 'till later. I just don't like the way it starts right now nor how much it hits. If I wanted that I would have bought a CR or RM... but I bought the RMX. I got got it for a good deal and knew even if I had to replace the entire top end completely I'd still be OK on the deal is all and that's why I bought it anyway... plus, there wern't any others I could find for a least 400 miles in any direction.

 

[placelast]

I'd conclude from what you've described it's the starting circuit; it needs more fuel when cold but once warm the mixture is correct for the starting process. The best move would be to replace the cheapo PJ with a more sophisticated PWK, but that is only if you are going to keep it and don't mind spending $250 new or ~$100 used. I have the PWK on both of mine.

A new barrel is shy of 400 clams, a new pipe for your type of riding would run another 200. If you go that route then look me up and I'll cut that in a third. All I'd want in exchange is the $ and your exhaust. I ride in the SoCa desert so a big-hit delivery from the FMF is fine. [email protected]

The barrel is coming off of my son's low-hour (original piston, in specs!) '90. It has a mellower hit than my '97; as a matter of fact it runs like an uncorked KDX or four stroke, having an even power delivery from the bottom to the top; mine has more snap and runs like a slightly underpowered, heavy flywheeled MXer. Being a young whippersnapper he wants my engine's characteristics so I'm putting on a newer barrel I ordered, and extra FMF pipe I have. I'd swap barrels with him but we don't do that much woods riding to justify tuning mine into soley a woods-oriented machine. And I'd hate to see his barrel go as I like riding his bike - the way it runs so cleanly in the woods, but then again we don't do that often enough to justify keeping it that way.

You may want to consider a Steahly fly wheel weight to smooth out the hit and minimize stalling, especailly when using the rear brake. I have one on each of ours since we do rock gardens in the desert and sometimes mountain single-track; makes it hook up better and tames down the delivery. You are welcome to try mine to see how you like it before spending the $.

There is nothing to be ashamed of in owning an RMX. It was the last asian 250 2-stroke enduro imported. Yes, they are not new tech and there are superior offerings from europe these days, but as a package and for a lot less $, relatively speaking, it delivers well-rounded, do-all off-road versatility.

 

[CyberChrist]

So you mentioned that you think it's the starting circuit. I guess I'm not entirely positive what that is on this carb. I've got the slow jet, main jet, needle, and air screw... my understanding is that the starting range for this beast would be only effected by the slow jet and the air screw correct? Am I missing something in there? The manual is pretty much entirely useless to me in this regard.

 

[Stew312]

Don't forget to take a quick look at your reeds also before you rip apart the carb. Bad reeds = hard starting.

 

[CyberChrist]

Well, I think I solved the problem. I'll wanna check it over the next few days and see if it stays fixed, but basically I went completely through the carb and did more than just the cursory spray with carb cleaner this time. Dissasembed the whole thing and soaked all the metal bits in carb clean for 30 minutes (making sure to keep all rubber out of course!) and then cleaned and cleaned and cleaned, spray out with air hose, repeat. Took about 3 hours to get all the varnish off and everything looking good as new. I also pulled the reeds and made sure they were OK... they were, and pulled the plug, turned the bike upside down, put her in 4th, and turned her over for a minute or so and evacuated about a cup of gas outta the crankcase. Freaky, it didn't evacuate it when it was running... my NSR racer always would... anyway, then made sure the float height was dead on and bingo... when all was buttoned back up she now fires on the 1st or 2nd kick, no throttle. :) I'll probably re-ring it just to keep her snuff as she only pulled 140 dry and cold for compression (180 with a squirt of oil) and that's good enough, but I'd rather not screw around with compression for a trail bike.

 

[brandolph]

Could you're fuel shutoff be leaking? My RMX always started easily until the petcock went bad. Took me months to figure out what was happening but the thing took twenty plus kicks to get going after it sat for a day or two. Started great when warm. The petcock had a slow leak and even with a good needle and seat the bike would flood itself. I've heard the old Suzukis are famous for bad petcocks.