still trying
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Have ridden a few trials now. All is going really well. Have got the breaks working better. As there are no springs in the front shocks, (saves 3/4 of a kilo!!) I've played with the "spring rate" a bit, and now is really good, way better than they were at standard. Nice and plush at the start and progressively, stiffer to the top. How this works is set the pressure by the minimum required to just return the forks to fully extended while bike is standing at rest without rider, (mine is 3.4 bar). The oil volume sets the fully compressed pressure/force, (less air volume when extended (i.e. more oil) = greater rate of force increase, i.e. compression). This has been a really enjoyable project with a great result (lots learned and a ridable bike), hope it inspires you to have a go in some way. Setup phase Have had stiffer springs fitted, increased dampening by 30%. rear is almost right. A bit stiffer at the top end and will be good. I've now added small springs inside the main ones that push on the shock bump stop and engage for the last 10mm shock travel, (the last 35mm of wheel travel) seems to work a treat. Steers really well, still good for drop-offs. (Was concerned about that) Nice and tractable. Easy to balance. Breaks; (should be called drags) typical drums. They actually work ok, I've been spoiled by discs. Clutch; A real mans clutch...Heavy. I last about three laps, need to relearn the old ways! Very difficult to make lighter, will need significant mods, so for now its cement pills and harden up. Motor; Smaller dia pipe and twice as long, with as much off the flywheel as possible. power is nice and smooth, with very good low down pulling power. accelerates as good as ever.Its a balance between flywheel and pipe.
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Does the motor have an expansion chamber creating a power band, (This is not desirable in trials, go with a long parallel pipe, and not too large, slightly smaller than enduro spec. I will increase the back pressure slightly and that will help the motor build torque). The big thing is smooth power and torque growth as revs climb, and as much low down torque as you can get and still have reasonable acceleration. So, no expansion chamber, heavier flywheel maybe, (try the std one first for a while). I had good results with a smaller diameter and longer exhaust pipe and lighter flywheel. Motor was a KT250 so already a trials unit. when riding you will (98% of the time), be trying to get or keep tires gripping the ground, so sudden uncontrolled bursts of acceleration from the rear wheel is not helpful. Typically you will need short bursts of acceleration to get over "stuff". at these times you will be "pushing down" with your weight through your legs to increase grip to handle the power increase. The timing of these two actions is half the battle, balance being the other. Oh and then there's stopping, reading the section, mental self control,.............But I'm sure you've got all this already, Good luck with the build, bet your learning heaps, I did with mine.
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What was the repair?, and how much of the motor did you pull apart. Also how was the damage done, (it may have resulted in other issues). If the motor was fully dismantled then there could be something binding and stopping the selector drum moving. Really need to see the motor selector assembly with cover and clutch removed to make a decent guess.
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just beginning again, which trials bike?
still trying replied to crankcase's topic in Classic Trials
For learning on, go modern. All brands are good, just give each a try and find one that feels right, If the bikes is in good condition , even as old as 2010, will get you a modern bike that has good handling, suspension, breaks, clutch etc. The modern controls are much easier to operate. The breaks are way better and consistant. the power and clutch way better. Maintenance wise, there's less to do. And yes 20kg lighter is a big deal. The two strokes definitely do not need frequent rebuilds, even if you thrash them. Mine has done expert grade for three years, left in the shed for 17, dragged out, given new air cleaner, changed the fluids and away I went, so far for the last 7 years, (its a 1995 Gas Gas JT35 (327cc) ). More modern bikes are far better than mine that's for real. And its easier to ride than my KT250. -
If the rubber shows no signs of degradation powdering etc, and holds air, then they would be worth using.
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HELP NEEDED Can anyone identify this twin shock bike please?
still trying replied to Robbro's topic in Classic Trials
Does look like a Honda XR200a tank, Nice build by the look of it. Good luck with yours Ftwelder, also looks cool. Awsome to see creative bikes, especially when the finish and fitting is good. -
I've run E10 petrol in my KT250 for years no problem. But I also rebuilt the motor (using std hydraulic industrial rotary shaft seals) back in 2013, and have no problems. fuel line that i use is polyeurethane airline tube from SMC, and was expecting to be frequently replacing it, but am still on the first tube. Its colour has faded a bit, but no more than when used as airline. I guess what I'm saying is try to use compatible materials where possible and plan "end of life servicing" as standard maintenance, and you will have no problems when out riding.
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you could try acetone. I have used it on carburetors that have been sitting with dried two stroke petrol for 40 odd years, and it worked. Not quite black sap level of crud. If you do try acetone, I would think the same procedure as you did with petrol would be the go. I have recently restored a '70s Honda TL250, (ali tank) and its tank looked like it had a coating of some sort in it, (Black/ dark brown in colour ), I thought it may have been a sealant or protective coating (it was all over the inner surface to some degree) so washed it out with petrol as you did and left it. So far no problems.
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For me; I'd go for a Fantic 200 or 240, nice and light with good handling. The ones I owned "back in the day" were as reliable as the Yamahas' and Hondas'.. Once you get used to it the kick starter it is much easier to use than the conventional ones. I have no idea about parts in the US, but getting bits from around the world these days is pretty good. Honda TLR250 would be best, Yam TY175, nice and light, and can be setup really well, with some careful research. SWM twin shocks were also really good in their time, along with Montessas', and Bultacos'. Without knowing you fitness, off road experience, etc, I would suggest go for; light, nimble, with predictable power, and good breaks. Most of the bikes are pretty reliable as long as they were/are serviced properly. Good luck with your search
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Here's a thought, Which lasts longer, Spending the day enjoying riding a trial, or finding out you've won. I find that if I've won it feels good for a few moments, but if I've had a good ride it lasts days and makes me want to ride some more. As old bikes are few and it would be good to have the sport/class survive, accurate replicas should be allowed. They Must use the same technology as the genuine bikes.
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here's a thought; Is winning that important. Or is enjoying riding your machine the point.
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Beautiful build, Well done, now get it dirty.
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Sorry about the delay Tony, yep its the same one. When I took a break from trials in '97, I knew if I sold it I probably wouldn't get back into trials. Might start looking for a more modern bike soon, but also keen to pick up a '70s TL250. I'm fixing one for a friend at the moment, what a cool beast for twin shock trials.
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I ride a 1995 JT35 as my "modern" bike, and yes there's quite a difference to the modern stuff. Seems like about 2001 there was an upgrade (better brake, clutch feel and weight loss), , again around 2005-10, and the latest bikes with fuel injection and active electronic engine management are another step up.
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If your looking for the flat type seal. I used one out of a plastic 20lt can cap, (look around the caps come in several sizes), and are generally chemical resistant. Note; anything that has rubber or silicon in its makeup description may swell when in contact with petrol.
