jse

O.K., I think I get your point (although you lost me on the last sentence), I'm yapping about "theory" and what this guy needs is information concerning "practice". First, contact your dealer and get the actual suspension travel measurements, front and rear, for your particular make, year and model. Figuring a third of that is easy. It will also depend on the type of fork, so they are not all the same, for instance a TECH fork has about 165mm of travel and a 40mm Marzocchi has about 177mm of travel. Measuring the fork setting is fairly straight-forward (measure on the tube) but rear setting is a little tricky. The rear wheel does not move straight up and down, it moves in an arc around the axle pivot, so you measure from the center of the rear axle to a point, maybe 4-5" forward of straight up on the fender (the measuring tape is canted forward at the top), which will give a little more accurate measurement. When you measure sag on a RR or MX bike, it's usually butt-in-the-saddle. A Trials bike does not have a "saddle" per se, and I like to set sag with the rider standing up and placing enough weight on the bars to mimic the approximate stance he/she would use riding (if you don't weight the bars, the front will probably be closer to 1/5th travel). If the sag is close, the bike will lower and raise front/back equally when the rider bounces, also placing weight on the bars in the process. Does that help a little? Jon

What year and type 250 do you have? Jon

I'm guessing that a lot of riders think there is a "perfect" setting for their bike, which I don't believe is true. Sure, you want the sag to be in the ballpark and close as possible to factory recommendations as it has an effect on the geometry of the suspension system as it was designed. There are a lot of input variables for Trials suspension due to the way we ride and it is quite different than setting up a roadracer or MX bike, which I know from experience. Proper (reasonable) sag settings are just a beginning, but it gives you a "baseline" to start from and eliminates a possible variable that can cause problems. It's probably the first thing you want to check and set when adjusting suspension. If there is too much race sag on the rear, for instance, it will affect a measurement in the front called "trail" and that will have a dramatic effect on the way a bike steers. So I don't think you need to get sag down to the exact millimeter, but you want to get close. This way the suspension works as designed and you'll spend a lot less time and effort compensating and more time enjoying riding. Jon ps. The suspension tips on the GasGasUSA website is one of my old articles I wrote some time ago for our national Trials newspaper. It was a general overview without getting into the deep tech stuff.

I usually like to run the engine for about 15 minutes just to check things and then let it cool off. Check the coolant level just to be sure. Then the easy way is to take it out for an easy section ride, avoiding heavy load or high RPMs. I ride about 15 minutes and let it cool off 2 times and then it should be ready to use. Keep track of engine temp (usually not a problem) during break-in. Some riders run a slightly richer premix ratio during break-in (say 50:1). The initial low-load, on/off throttle riding in an easy section is probably the best way to bed things in and avoid "hot spots" on the piston. Be sure to re-torque the cylinder and head fasteners. The head capscrew copper washers will compress slightly at first running and re-torqueing them will avoid o-ring leaks in the future. It's been my experience that most oil leakage and o-ring failures on a new bike can be avoided by just going over all the fasteners after a few heat cycles. Jon

I use just a "whiff" of throttle under those circumstances. Jon

Here's what I've found: The radiator and fan assembly are available as separate units. I think the problem may lie in the fact that the fan and shroud can only be bought as a unit and the fan/shroud/radiator can be bought as a combination item which is what may have lead to the confusion on the part of some dealers. As an aside, we just put a new type fan/shroud on a 2002 Pro with little problem. The shroud fits fine but the connector was not the same so the fan was wired in (easy two-wire black/blue connection) the "old way"-directly. The fan blade has a wide "center" that acts as a shield for the motor. It works great. Jon

I've also been told the same thing but it doesn't seem to make sense to change from the separate units that were available prior to the new round tube frame. I've got an inquiry in to the importer to see if this is, in fact, true. Jon

The 05' 300, and sometimes the 04', did seem to have hot-start issues, which may be related to the stator windings. You might try closing the plug gap up in stages to see if that helps and if it does, perhaps a new or rewound stator will solve the problem. I know a change to an NGK BPR5EIX helps and they take less juice to fire, which indicate a weak stator output as at least a possibility. Jon

You'll need to pull the sidecase off and have a look at the kickstart mechanism. The bang may be a lot bigger if you don't. Jon

Well, sounds like carbon is not the problem and the pipe should be clean also. I've used Motul with good results. Since you know the previous owner, you might ask him if he had the problem prior. It may be poor/old fuel, which can give the same symptoms and would also make the bike a little more hard to start due to the loss of high-end aromatics. A complete drain and fresh premix would eliminate that as a cause. It also may be a fuel flow restriction, which would show up on longer hills quickly (low speed unaffected but the increased fuel demand/carb angle would lower fuel in the bowl), so you may want to check the float level, petcock filters and flow and carb filter. Obviously it could be electrical, so a throughly cleaning/inspection of connections and grounds may help (always do the cheap/easy fixes first so fresh fuel is next). One time at a World Round I had a minder's bike do the same thing and finally found that the core in the muffler had broken and shifted, which restricted the exhaust internally (you couldn't really tell by listening to it however) but that was a weird thing I'd never seen before and I doubt that's your issue. Jon

Interesting. The pilot and needle setting are on the rich side, indicating that the previous owner probably had the same problem (and was trying to compensate for it). The main is good, #118 works well in most cases and pilots are usually #36-38 and needle is generally #2-3 groove. You'll want to make sure your floats are correctly set and say, not binding. I would guess that the jetting is not the problem but you may have a buildup of carbon in the combustion chamber that would raise the CR to the point that a load would cause the pinking. If the previous owner ran an older type premix oil (a good oil, just not suited to the low RPM, on/off throttle settings in Trials) that promoted carbon buildup. If it were my bike, I'd pull the head off and clean the chamber throughly as a first step in diagnosing the cause. Since you don't know what oil was used previously this is only a guess. Most of us run a full-synthetic but you would be surprized at what some riders run in their engines (usually because it always worked great in their old 1974 Bazooki MX'er).. A restriction in the exhaust system will also cause this symptom (maybe even oil-related carbon buildup in the head pipe just where it attaches to the cylinder). A 5-range plug works well in Trials bikes, such as an NGK BPR5ES or better, NGK BPR5EIX-11 set to .024". Jon

Is it a "Pro" or the "Edition" model for 2002, they are quite different. Jon

What is your current jetting map? (main, pilot, needle, slide etc.) Maybe we can figure out if that's the problem as I don't think Preminum at 70:1 should require adjusting under most circumstances. Jon

Correct. And pushing down on the tensioner block to reduce tension on the chain makes adjusting the axle cam a lot easier. Jon

Other than actually measuring center-to-center rear axle/swingarm pivot, a quick "tell" is to look down the upper chain from the back. The chain should be absolutely straight from rear to counterhaft sprockets and any "bow" to the chain run will indicate misalignment. Jon

10mm left on a stoppie is about right, you don't want them to bottom out completely or they have no reserve to absorb a further hit. What is the rear race sag? You also need to ride for a bit to test them as it's not unusual for a rider to compensate for bad suspension and your riding style may change slightly with the new preload setting. Depending on how things turn out, you may want to go another 10mm off the preload spacer and add about 20cc's of oil to the forks. This will reduce preload stiffness and provide some bottoming insurance. Jon

John, I'd go down to about 75mm. If you have a little problem with the forks bottoming on big dropoffs, we'll look at raising the oil level a bit to compensate. Jon

John, If the forks are too stiff, you'll want to cut down these spacers even if they are a standard length (I think these are an extra length but don't have an 04' pair to check). I think they usually run in the 60mm area for the 04', but not positive. How much do you weigh? Jon

You'll probably want to replace the inner and outer "races" of the needle bearing, which in this case will be a gear and a shaft. Maintaining fresh oil in the Pro usually prevents that split needle from going bad. My Pro is 10 years old and problem-free but I am compulsive about oil changes. Jon

The 02' 280 Pro takes 350-380cc's. It's different from the 03' and later Pros, which take about 425cc's. They were giving you info on the "Edition" model, which is the older type engine. Jon

" black carb top doesnt seem to seat fully on carb" The carb top only goes on one way, there is a tab that fits into a slot at the top of the slide tower. The cable enters the carb top to one side so if you put it on 180 degrees off, it would pull the cable slightly longer and if combined with a tight cable, would cause the slide to hang slightly open. You might want to check that just to be sure. Jon

The seal kit for the carb may help, especially the o-ring at the top of the slide tower. I'd check the cable to make sure there are no kinks and there is a little slack in the adjustment. Look in the throttle housing to make sure the cable is not frayed at the end. You may want to pull the flywheel to see if you have oil weeping from the seal. If it was a trans side seal, you would notice a drop in tranny fluid and lots of smoke out the exhaust. It's not unusual to have a manifold leak as they are easily overtightened and this causes "bowing" of the manifold between the bolt holes. What is your jetting, especially the pilot jet and slide #? Jon ps. In my experience, the Iridium BPR5EIX plug is worth the extra money-they require less voltage to fire, have a slightly extended heat range and resist fouling to an amazing degree. The last one I had in my Pro for 2+ years and I only changed it out of guilt, not because it showed any wear. I run them in my TY350s with equally good results.

The tube all across the lever end might just be too slippery also. You might use a 1/2 to 1" length just at the end so that the center of the boot sole catches the inner edge and acts kinda like a "V" that will keep the boot from sliding off. If you use grub screws, they will have to be quite shallow so as to not weaken the lever and cause it to snap off. Jon

Baldilocks, Some background on the T-vents and to explain Copey's observation: We used to have some serious issues with the MX/Supercross bikes bogging on the first ramp on the steep double/triple jumps and traced it down to accumulated fuel in the long vent lines being sucked down/out the tube when the bike hit the steep uphill for the jumps. This would cause a quick drop in atmospheric pressure in the float bowl and temporarily cut off fuel to the engine at the worst possible time. The sudden loss of power would cause the rider to short jump and miss the last landing ramp, often "casing" the bike, or landing directly on the skid plate, which does not allow the suspension to absorb the shock. This is like dropping several stories and landing directly on the ground and resulted is a lot of shattered bones and careers ended. We started adding a "T" at the vent outlet and running extra lines up to avoid this and Keihin later added this feature as standard to the carb body. That extra vertical T vent outlet is probably not as necessary for Trials use, but is standard on most carbs now. Jon

Just be real careful with the top two nuts. If they are too long, they will wear a hole in the fuel tank. Jon