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Finding a source for a piston and rings is difficult and I haven't found one yet. I've posted it on this forum and didn't get any good leads and am tempted to convert my 350 to a 250 due to availability of parts. I'd be interested in the 90's mods. I'm not sure how rare the Talon conversions are here in the U.S. Some riders swap later front ends to the TY for a disc brake. Jon

Sam, You will need a CDI set up for it, you just can't add it to any bike. The 2005 GasGas bikes came with two wires, an orange on and a black one with female/male connections, up under the front of the fuel tank. These could be connected/disconnected to give the two pre-programmed ignition maps that differ abpout 2500 RPM, one with a steeper rise. In 2006 the sun/rain switch was added to the handlebars. 05 bikes can just have the switch added to make it like 06 on up. Or just add the switch to your bike and fake out your buddies.... Jon

The lip is machined off, but the squishband is also re-machined up into the head. I run the .003" copper gasket with this head. The volume in the center chamber is deceptive when compared to the stock, cone-shaped chamber as the "roof" of the chamber has also been dropped due to decking the gasket surface (removing the "lip"). You could possibly run the lip removal and thin gasket, but you will need to check the squishband clearance carefully and each cylinder/head is different due to manufacturing tolerances. The porting is different due to wider/re-shaped ports (increases bottom/mid-range torque) and the port timing is "staggered", in that the rear boost-port opens first, rear transfers second and front transfers last, which promotes better scavanging of the cylinder. The exhaust port is widened and re-shaped accordingly. The pipe is slightly larger in diameter for better volume and slightly longer to promote mid-range torque. Leaving on a certain amount of flywheel band smoothes out the power and is much better for traction in some sections, such as a muddy uphill where you can roll on the throttle to get quick response where the traction is good and then use trailing throttle (and flywheel) to roll over the bad spots and still get good bite from the rear tire. Jon

A friend just sent me this link: http://blogs.denverpost.com/captured/2010/...ters/#more-1547 with some unusual photos from the real Pacific. Most of these I've never seen. Jon

ZO9, Thats about right on the peg relocation. I'm not sure about the 250s, the U.S. got the 350s exclusively from what I remember (we tend to like engines large here, in spite of our inability to handle them at times) and may be the only ones with the extra flywheel weight band attached. I'm sure our UK buddies can answer that. The 350 had a trapizoidal shaped shaped combustion chamber which was the rage at the time (it was designed to reduce overall surface area in the chamber). The chamber design was not too bad but the excessive squishband clearance was the problem. Most of the 350s I measured ranged from .084" to .097"+ and should be in the .039"+ area. Some riders removed the thick copper gasket and used sealer to secure the head to the cylinder in order to tighten up the clearance. This technique was not unusual and we used it often in the roadracing two-strokes at the time. The problem with excessive squishband clearance is, you essentially have two combustion chambers. With too much fuel/air trapped in the squishband, the spike in pressure/heat when the plug ignites the center chamber tends to autoignite the fuel around the outer area of the piston crown. This results in the familiar pinging ("pinking" outside the U.S.) of the 350s. Pinging carried to extreme is detonation, which is a real engine killer. Probably a better way to re-set the squishband clearance is to get some very thin copper sheet (hobby stores carry some) of say .003-.006"" and make a new gasket. I've re-machined my chamber to a more effective hemi design (the shape and volume goes along with the different porting arrangement of my cylinders) and along with the .003" copper gasket, it brings up the clearance to .040". Jon

The 1985 TY350N was a little different animal than the TY250s available in Europe. For instance, it used the 8-petal, steel-reed cage with no "stuffer" that really killed intake velocity and affected low-RPM carburation. That, coupled with the huge mass of the crank assembly and the larger piston made it fairly "wheezy" in the throttle response department. The crank assembly was designed for the big-bore MX bike and in addition a thick steel band was shrunk-fit on the flywheel. A lot of riders have the band machined down to reduce the rotating mass. Some cut it off completely but I've found that machining about half the thickness seems to work better. There are several ways to relocate the pegs. I cut the peg bracket off the frame tube and made a 1" extension, rolled from mild steel to drop the pegs lower and back. Adding a serrated strap of steel to the back of the stock peg locates the sole of the boot further back as well as widening the peg for comfort and the combination has proved just about right. Jon

Ron, I tried to sneak it into my trailer when you were not looking, but I think you and the new owner were on to me........ Neat bike, lots of original thinking went into the frame/components design and with it's proven engine, it should do well. Jon

Kevo, Here's some suggestions, and I'm sure others will have some also: You have the large "tapered" bars (sometimes called "fat bars") common to most modern Trials bikes. I use a high bend Hebo bar (GasGas part #HR30009285P") and S-3 makes a nice bar clamp that raises the bars and has more adjustment that you might want to look into. Riders here usually use Type-F ATF in the transmission, DOT 3/4 in the brakes, Magura mineral oil in the clutch (available from your GG dealer, KTM dealers and some mountain bike shops) and a full-synthetic premix oil at about 80:1 ratio (I use Castrol TTS in my bikes with good results). Your bike comes with a kill-switch. Standard plug should be an NGK BPR5ES (I use an NGK BPR5EIX set at .024"). There's a start. Jon

Ah, yes, and just about any two-stroke Trials bike today. From what engineers have told me, modern two-stroke pistons have cam-ground diameters and tapered sides to cope with the unusual temperature extremes (hot exhaust on one side and cool intake on the other, as opposed to the generally uniform temp ranges in a four-stroke piston). When they reach operating temperatures, they expand to the basically consistant circular diameter and straight sided shape we would expect. Jon ps. And, no matter how much I whine, cry, complain and throw myself on the floor, the wife says no NR......

I don't remember the carbs coming with a clear plastic floatbowl but it could be an aftermarket item. Check with your dealer, he/she may be able to order you a new bowl. The chassis VIN number should tell you what year the bike is. It will start with "VTRGG" and the 3rd and 4th numbers after that will be the year, for instance,"97" will be 1997, "98" is 1998 etc. Sometimes a bent shift fork can cause your symptoms but usually it's a problem with the shift mechanism/shift roller. As for the clutch, it may be the pressure plate was not aligned correctly (there is usually an "X" on one of the spring towers that aligns with a mark on the plate) or the "mixed" disk (the plate with fiber on only one side), if it has it, was not put in first. Jon

Bob, If at all, try riding the bikes in question. You're not a beginner and I would guess you would adapt fairly quickly to a two-stroke. I know of two riders in their 70's who ride Ragas and really like them. I also know of several riders who are wary of the Sherco 3.2 as they say it has too much power for them (!). Each bike seems to suit a riding style but most riders can adapt their style to suit the bike and often can do things they had difficulty with on their other bike. Trials riders are usually more than willing to let someone try their bikes so try each one to see what suits you better. Jon

Be aware that the heat range numbers are opposite between the NGK and Champion. The "7" in a Champion is quite "cold" and you need in the "10-11" range, which is roughly equal to a "5-6" range in the NGK. Jon

Bummer, not had one that bad.....yet. You might have to grind the nut down and just before it's totally gone use a pin punch to knock the bolt through. Jon

Unfortunately, you've come across probably the most overlooked bearing on a Trials bike. Riders will service the dogbone bearings and think they are o.k., but the bearing in the swingarm is usually not noticed. You'll probably need to drive out the bolt with a long, thin drift or piece of rod. Count on replacing all the parts as you'll most likely find rusted pieces. The inner bushings go in from either side (they look like top hats, and it's a good idea to look at a parts manual to get an idea of how the parts are assembled) and use a thin drift with the end cut square so you have a sharp edge to catch the bushing in the center of the bore and drive it out. Unless you plan on taking the swingarm off to press out the bearings (not a fun job) you can make a simple bearing removal tool with a short length of threaded rod and two long sockets. The smaller socket should be slightly smaller diameter than the bearing shell and the larger socket should have an inside diameter large enough to contain the bearing shell when it is pressed out. Thread the rod through the bore, tighten up the nuts and the small socket will press the bearing shells out the side and into the larger socket. Lots of penetrating oil helps. You can also use the tool to install the new bearings after you've carefully cleaned out the bore. Jon

Yea, you're right, I forgot about that, they did quite well. I was thinking GP, but the bike was a very good endurance racer. Maybe I can con my wife into buying a historic endurance racer. Hmmmm, probably not, darn........ Jon

I would think so. They are fairly rare, I think only about 200 were made. The NR is the later street version of the race bike, which did not dethrone the two-strokes as intended. It didn't do much on the race track but it did cement Honda's reputation as a technological giant at the time. I already talked to my wife about us making an "investment in motorcycle engineering history" that I could proudly display in my shop. She said "fugitdaboudit" in no uncertain terms........... Jon

As I understood, the NR750 (actually the "RC40") was built to comply with international roadracing rules that limited the number of cylinders the engine could have. The NR's V-4 is essentially a V-8 with conjoined cylinders. The engine had 8 valves per cylinder (and 2 plugs, 2 connecting rods, 2 injectors etc.), which addressed the problem of reduced volumetric effeciency with larger valves in larger cylinders. The bike was not that successful as a racer, but sure showcased Honda's ability to "build it because we can" corporate philosophy. There are a few of us still around that remember the legendary RC166 250/6. I would imagine that parts are quite dear at one's local Honda dealer......... Jon

I'd try the easiest things first (exterior modifications), such as a black tube Domino throttle and 10T front sprocket. Try each change before stepping up to the next to see if it gives the results you want. The base gaskets will change the port timing, increase the squish clearance and lower the secondary compression. The spacer will do the same, except for the port timing. Jon

I agree, Kev is a wealth of knowledge and should be able to fix you up with no problem. Jon

Gordon, Here's the spec.'s from the TrialsPartsUSA website: 2000/01/02/03 TXT280, TXT280,TXT321, TXT280

Ron, http://avtatrials.com/ rider's meeting at 10:30am and don't forget to set your clock up an hour. Let us know how it works! jon

Hello again, Wayne. I just saw this post after I sent you a link to the Ducati wiring diagram on your e-mail account and some info as to what type of switch to use and where to mount it. Cheers. Jon Oh, for others: the 94-96 Ducati wiring diagram at http://www.trialspartsusa.com/tech.html , a Yamaha YZ250 two-wire switch, one wire to the black wire on the CDI and other wire grounded to the CDI mount on the frame and mount the switch in the center of the bars so it's protected and easy to get to if the left side of the bar is buried in water, brush, rocks or mud. That position also makes it a little easier to reach the muffler end to shut down the engine if it goes WFO.

Wayne, P.M. me and I have one that might help a little. It's in Spanish and a little hard to read, but you should be able to get some info off it (829 Kb, Adobe file). As you probably found out when you first tried to start it, the compression is fairly high so use a good grade of fuel. A full-synthetic premix oil at 80:1 works well in the mid-90's big-bores. Jon

It can get kinds confusing. My guess is it was a "Blaster" engine (single, air-cooled Yamaha) and that might make a reasonable unit for the bike. I'm not against changing or modifying bikes, heck, I'm always doing some weird project. I guess I'm for having the highly-converted bikes run in their own class rather than in the "pure" twin-shock class. Twin shocks are pricey enough, but theres always someone that will do something like shell out the dough to convert a new Pro just to win the pi**ing contest. I know what goes inside some of the Pre-65 bikes and I just would hate for the rules to be wide open for the twin-shocks. A "run-what-you-brung" class for twin-shocks would allow for creatiive engineering. Maybe I'm too simpleminded....... Then again, Trials is about the rider's ability rather than the machinery to a large degree, so I can also understand allowing leeway in the types of bikes. Jon