rockgardener

Thanks for the clarifications; I understand much better now and will take extra measures to baby my Pro's transmission!

Okay, so you're saying I shouldn't shift my GasGas like I do my KTM's, but I still don't know what I'm supposed to do instead. Do you mean that I should do as little shifting as possible while trail riding, or that I shouldn't do trail riding at all on this bike? I'm new to trials, but I just attended a two-day trials riding school and learned from multiple instructors that I can be much harder on my GasGas clutch than I would have ever imagined - I'd never start a huge hill climb from a standing start in third gear on one of my woods bikes, and then slip the clutch the whole way up, for example. But that's how we were taught to do it on a trials bike at this school (and it worked great). Same thing applied in lots of other situations, too, and I developed a very different relationship with my clutch than I'd ever had on any dirt bike or street bike before. I now do much, much more clutch-slipping on my trials bikes (I have an old Montesa 315R, too) than on any other motorcycles. I understand (a little) that in competition, a trials rider most often selects a single gear for the section at hand, and just stays in that gear the whole time, relying heavily on the clutch instead of shifting up and down. But nobody at the school said anything about trials transmissions being fragile and unable to take the stress of "normal" shifting (and we even went on a trail ride with one of the instructors at the end of one day). Is this a GasGas issue, or does it apply to all trials bikes?

Thanks for the feedback, lineaway. I'm relieved to know that these sounds may be normal, but I'm concerned about this need you mention to be "careful" during high-speed trail riding. I'll certainly exercise care, but exactly what should I be careful about? I don't do clutchless upshifts or stomp on the gear change lever or anything else that can be hard on a transmission (that I know of). But maybe I'm unaware of something that can be harmful in this case, so please educate me.

Just spent an afternoon doing some relatively high-speed single-track trail riding and noticed two odd noises: 1) shifting from third to fourth produces a dramatic CLUNK, and 2) fourth gear whines loudly, unlike any other gear. I've only had this bike a short while, but never noticed these noises before. Then again, I rarely went past third gear, so it could have made these sounds and I just didn't notice. Are these normal for a 2012 Pro with less than 15 hours? I recently replaced the oil, which was ATF, with more of the same (about 400cc or so - level is 3/4 up sight glass). I don't notice any difference in clutch action. Thanks for your input.

True, the Honda steel plates will work fine -- they're dimpled just like the Apicos. But they're MUCH more expensive - about THREE TIMES the price of the Apicos. And, since nobody is complaining about the Apicos, I can't imagine any justification for spending the extra money on the Honda plates, unless you simply can't figure out a way to purchase the Apicos. Again, I got mine at BVM, no problem; just Google BVM trials parts.

After trying three different types and levels of tranny oil, back-bleeding and readjusting the clutch several times, leaving out a couple of pressure plate springs, and several other superstitious "fixes," I finally popped in a set of Apico dimpled steel plates today (with everything else returned to stock, and Dextron III in the gearbox). The difference is amazing! Zero drag at startup, nice strong engagement, but the most impressive change is the smooth, linear transition from disengaged to engaged - nothing at all like the abrupt, jerky action of the stock plates. I'm not sure any of the other mods really made a significant difference, but this one is unquestionably a major step up. It now feels almost as silky as my new GasGas Pro's clutch, and before it had been nowhere close. I highly recommend these; got mine from BVM - quite reasonably priced at about $26 USD, and certainly worth much, much more for the difference they make. What can I expect over time - does this brilliance fade?

Steel fork is a Paioli, not Sachs.

Trials newb here. Just got a very slightly used 2012 250 Eco at a great price. Trying to get clear on differences from the 2012 standard Pro model. See if I've got it right. Engine internals are the same, but frame is from 2010 Pro model. Fork is steel Sachs unit, instead of aluminum Marzocchi. Header is steel, instead of titanium, and muffler is all-aluminum instead of aluminum/composite. Rear wheel is rim-band-type instead of having spoke flange. Rear brake has separate master cylinder and remote reservoir, instead of integrated unit. Tires are Pirelli instead of Michelin. Airbox is small, instead of new larger design. Plastic is 2010-spec, with different stickers. Is that a complete and accurate accounting? Why is there no official description of the 2012 Eco on any of the Gas Gas websites? Many thanks for your knowledgeable replies.

Finally got out on a practice course for the first time on my new-to-me 2001 315R and really loved it! Problem is, my 17-year-old loved it at least as much as I did - I almost had to wrestle it away from him each time I wanted a turn. So, now I'm looking for a second trials bike so we can ride together and not have to take turns. The only bike currently available nearby is a 2001 Sherco 2.5 (looks to be in good shape). Can anyone tell me how that machine would compare to my 315R? Thanks for your insights.

Thanks for the replies. I've fitted my petcock with a little chain (loose end anchored with a zip tie to the clutch line) so that it's now very easy to pull down and push back up. Good to know this is something to watch closely, and that my bike isn't the only one.

So I need to be more careful to turn off the fuel petcock when working on the bike. And I could have removed and cleaned the spark plug. But I don't know of a bolt to empty the crank case. Do you mean that fuel could have actually poured through the carb and reeds and collected in the crankcase? Where would this drain bolt be? I only know of the gearbox oil drain bolt. Thanks.

About 50 more kicks with the throttle wide open finally brought the engine to life, so there's no question about what happened - the bike was severely flooded. I wouldn't have thought such a small pitch forward would have created such a dramatic problem. Is this normal for these bikes?? Is there a better way to get them started after such a flooding?

My new-to-me 2001 315R has been starting FIRST kick every time since I got the carb sorted a few days ago. I've still only been able to putt around the yard with it so far, but it's been running fine. I put it up on a work stand for the first time to lube the chain. The bike was at a bit of a nose-down angle, with the rear wheel off the ground. After lubing the chain, I realized a big puddle of fuel was forming under the bike. There was no sign of any fuel leak before this, so I can only assume that the fuel was coming from the carb vent tube. (It was dark, the light was poor, and I had to rush out soon, so I couldn't thoroughly examine it.) Once the bike was back on the ground fully, the leak ceased. I tried to start it, just to make sure everything was okay, and it wouldn't even begin to start. I kicked it many times with the choke off and zero throttle (it had been running a short while earlier and was still slightly warm). Then I tried kicking it many times with the throttle wide open to clear it out, in case it was flooded. Nothing. Then I tried kicking it many times with the throttle shut and the choke on. Under no condition did it give the slightest hint of firing. I let it sit for several hours and tried again - still not so much as a cough. Just sounds totally dead. What happened? What's to be done about it? My two-stroke woods bikes will leak fuel through their carb vents when tilted far enough to the side, but it doesn't effect starting unless they've fallen all the way to the ground. Even then, a few kicks with the throttle pinned will get them running again. Are trials bikes so different? Many thanks for any help.

Bike now idles quite nicely after installing the new fuel screw o-ring. I can't be 100% certain this was the solution, since I gave the carb another thorough cleaning whilst waiting for the carb gasket kit to arrive. So I might have dislodged some gunk this go-round that survived the previous cleaning. Anyway, the change is dramatic, and I'm greatly relieved to not have to chase down and repair a main seal leak. Thanks to everyone for all the help!

Even without the use of butane (see previous post), today brought an interesting development. As I was re-cleaning and reassembling the carb per the recently quoted instructions from a Montesa dealership mechanic, I noticed a discrepancy between the parts before me and the exploded view in the diagram. An o-ring and washer were missing at the inboard end of the fuel screw! When I'd disassembled the carb the first time, I assumed it was a complete unit, and simply took care to reassemble it as it had been. I didn't go through, part by part, and take a thorough inventory in comparison to the diagram. I couldn't find a properly sized o-ring in the assortment I had handy, nor a washer that would fit, so I went ahead and ordered a rebuild kit with all the exactly correct o-rings, washers and gaskets in it. Maybe all my troubles have been the result of this missing o-ring, as I'm assuming a leak at the fuel screw would result in the type of lean condition symptoms I've been having. And it could explain why turning the fuel screw throughout its range seemed to make virtually no difference in the motor's behavior. Hopefully, the kit will be here by the weekend, and we'll know if it does the trick. I'm going to wait on the butane test for now...

Thanks for the input from recent posters. I checked with the mechanic at the (somewhat) local Montesa dealer today. He assured me this was almost certainly a carb problem and advised that I begin by going back through it again with not just carb cleaner but also compressed air. He said that often the passageways are partially cleared by solvent, but require air pressure to fully clear. He added that it's necessary to cover one exit hole at a time to force all the air through the second exit hole when blowing out the choke circuit and the pilot circuit, as each of those splits into two routes when blown from the float bowl side. He also told me it may be necessary to run a thin wire through the pilot and choke jets to get them completely clear, even though I can see light through them already and the holes look nice and round. I may also go ahead and soak all parts in solvent to be absolutely sure they're totally clean. I'd have done this already, but the inside of the carb actually looked quite clean - much cleaner than many I've opened up. Three other things he told me to check: First, the tiny o-ring at the bottom of the choke jet must seal well against the float bowl - if it's hard, cracked or mishapen, it must be replaced. Second, he said the idle set screw (throttle stop) must not be turned in too far or it will interfere with starting because it will prop up the slide and produce the same result as twisting open the throttle while kicking, which ruins the mixture. Because I've been trying to keep the motor running by setting the idle high, I'm sure I've contributed to the starting difficulties on this count. Third, he advised me to set the fuel screw further out than the single turn that the manual recommends; he said to turn it out until 1.5-1.75 threads were showing, and use this as my starting point. So, I'm going to re-clean my carb and check these details. I will also use fresh fuel and spark plug, and will report back on my efforts as soon as I get time to complete them. If unsuccessful, I'll resume detective work on the cases, but I'm really hoping the dealership mechanic is right and this is just a carb issue... NOTE: I definitely do not have the 1999 PHBH26CS carb mentioned by naichuff, with the combined pilot jet and diffuser. There is nothing under/above my pilot jet. For what it's worth, my jets are as follows: 110 main, 35 pilot (slow jet), 60 choke ("by starter jet"), K270 needle jet. I've got a D37 needle with the clip in the third position.

Thanks for the latest replies. I'll swap out the fuel. Sometimes the easiest/simplest fixes are the ones we overlook.

Thanks for the replies. When cleaning the carb I removed all jets and sprayed all passageways, although I did not notice whether the pilot circuit spray exited at the two locations Lineaway specified. I can recheck. I forgot to mention that I also checked the float height and it was spot on. As for swapping carbs with someone, I don't know anyone else with a 315R. I have read there are advantages to using a PWK28 (Keihin or copy), and I'd be wiling to eliminate the carb as a possible source of this problem by fitting one of those, if that seems appropriate/advantageous to those of you in the know. Dom, I assume you are saying that the ignition/flywheel main could be leaking, even though there is no trace of oil or fuel residue under that cover, correct?. And I'm not clear on putting the breather pipe into a glass of water. What would I be looking for, bubbles? If it is actually sucking air in through that pipe, wouldn't I risk sucking water into the gearbox? (I suppose that wouldn't be so terrible if it provided a conclusive diagnosis.) There are two breather pipes exiting the cases. You're talking about the one toward the rear of the engine, right? Thanks again for the help.

Thanks for your reply, Lineaway. I bought the bike in a neighboring state and only rode it briefly in the parking lot of the dealer who was brokering the consignment sale of this bike. All I did when test riding it was check to make sure the transmission worked properly and the bike sounded okay while running through the gears. I don't remember it having this idling problem then, but I can't be certain. I did not check for main bearing play when I had the ignition cover off - not sure how to do this. Would I just try to move the flywheel up and down by hand? I didn't think an oil leak would have anything to do with it, but I'm lost here, so I included everything I noticed.

New member here, and this is the first post on my recently purchased 2001 315r. Sorry to start my forum participation with a novel, but I thought I'd better provide all the information I can about my mysterious problem. The bike is hard to start, and when it does tick over with the choke on, the revs go sky high. I have to hold the choke in a half-on position while the motor warms up to keep it from either screaming or dying (is this normal?). Once warm, the idle hangs after revving and warbles (1-2 oscillations per second) when it finally drops, which it does very gradually over about 5-10 seconds. However, to keep it running, I have to set the idle rather high; otherwise it dies after about 15 seconds. Adjustment of the air screw does almost nothing. The bike seems to run okay above idle, though I have nothing to compare it to, since this is my first trials bike. (It feels quite weak compared to my two-stroke KTM 250, but I assume this is because of the 315r's heavy flywheel and big differences in tuning - I did NOT expect it to pull like a woods bike!) I completely disassembled the carb and cleaned everything thoroughly. I also pulled out the reed valve, disassembled and cleaned it, and replaced the gasket. The reeds (carbon) looked fine after I removed some white waxy residue that was also on much of the reed cage (bad gas?). The rubber boot that connects the carb had no apparent defect. I pulled the ignition cover and there were no signs of a leak on that side, nor were there any obvious signs of a leak around the cylinder base gasket or right-side case seal. The only visible clue that something MIGHT be leaking was a very small amount of clean transmission oil in the center of the skid plate. However, that could easily have been left from a recent oil change, as the previous owner replaced the tranny oil prior to selling it. I have thoroughly cleaned the skid plate and the bottom of the engine, and will look to see if any more oil appears there. So far, this area has remained clean, though I've only ridden the bike about 10 minutes since cleaning it. It's no fun to ride a trials bike in the yard that won't run properly at slow speeds. I've been told that the tell-tale sign of a right-side case seal leak is that the motor will run more smoothly when leaned way over to the right. My bike does seem to idle ever-so-slightly better in that position (continues to warble, just less dramatically), but still hangs after revving. I've also been told to sprinkle baby powder around the gasket edges and then look for any sign of dampness, since a case leak on a two-stroke will involve both an inhaling and an exhaling action. This idea falls apart in practice, though, as I can't really get powder everywhere there might be a leak. I've also heard that leaks can be detected by spraying carb cleaner around the gaskets while the engine is running, but I don't know what I'm supposed to be looking for with that, and again, I can't reach/see all the way around some gaskets' edges. One other potentially relevant piece of data is this: I've read about a small air filter that was fitted to earlier model 315r carbs. My carb doesn't have such a filter, and the hole in the right side of the carb where it's tubing would go appears to be sealed and without function - carb cleaner squirted in there just fills it up and doesn't exit somewhere else. Nevertheless, the 2002 owner's manual (the closest to my year I could find online) clearly shows the sub-air filter in the routing diagrams, and there is a tab jutting off my rear brake fluid reservoir bracket that might have once been used to mount such a filter. I've read elsewhere that the sub-air filter was eliminated by 2001, so perhaps the diagrams in the manual weren't updated. Or maybe my sub-air filter is actually missing - I can't tell. My carb does look identical to the one pictured later in the manual, in the carburetor section, and there's no sub-air filter visible in those pictures. Assuming no more oil collects in my skid plate, how can I determine where the leak is? Could a missing sub-air filter produce the symptoms I've described? Many thanks in advance for your help!