dombush

All a long distance trial a few weeks back meant unusually that I used 5th and 6th gears. When 5th gear is selected the noise is "different" with a slight whine but nothing dramatic. Its the same in 6th but disappears as soon as I change down into 4th. The only other clue is that when I roll off / on the throttle in these gears it seems to have slightly more backlash and noise to go with it. I'm aware that the pro has a unique-ish gearbox design so I'm not unduly worried but want to know from other Pro riders if this is normal or not. Dom

Wow, watching those videos I really feel for the observers. Difficult to pick out a momentary stop (at least on video).

A. Although I haven't done it on a 125, Previous trials bikes geared up will reach around 35-40mph and still be "safe" to rider and machine. B. So long as you keep the revs to a reasonable level the mechanicals of the engine will be ok. The issue is that trials bikes are jetted very lean because in competition you can get way with it. Riders in long distance road trials often go slightly richer on the main jet to compromise between road and trial setups. The other common mod is to turn the choke on. Choke only works at low throttle openings so its common for riders to regularly "back off" the throttle opening to 1/3. This keeps the combustion chamber temperatures under control. C. Definitely need to change gearing. Many bikes will allow a gearbox (countershaft) sprocket with an extra tooth which is equivalent to 4 teeth removed from the rear wheel sprocket. You might also go down 2 teeth on the back sprocket as well. It isn't out of the question to change the gearbox sprocket back to the original when you get to the trial. You would need circlip pliers and a rear wheel spindle nut spanner. All said and done though... its a real pain in the neck and is best avoided if you can. But if you don't have a choice, do what you have to do. You may meet up with someone who will offer you a space on their bike trailer. Can I suggest that you read the Gasgas, Beta and Sherco SSDT setup advice documents published on this website. Many of the modifications described in that document are relevant with the added benefit of being specific to a certain brand of bike.

Man, tried negotiating that French WTC results website... someone got carried away with the colouring pens! Much prefer your dour understated greys and pastels Andy. Off to find some migraine tablets!

Throttle control in trials is pretty much the most important single factor. Pretty much agree with all the previous posts. Particularly the specific practice. I would invent some specific routines that force this to happen. I have a variation similar to Zippy's. Zippy suggested practicing working the throttle against the clutch, perhaps with the back brake on. You're doing well when your throttle control responds exactly to the load that the clutch is placing on the engine. A sign that this is happening is that the engine revs vary very little because you're throttle response is perfectly in time with the change in load. You need very little revs to achieve this (just above tick-over). The similar exercise that Zippy hints at is full lock turns (in a figure of 8 pattern). With the bike on full lock you cant move fast without falling off, this means that even first gear at tick-over may be too fast. This then forces you to slip the clutch as above, but with the added balance / control of turning thrown in. Success is when you have full steering lock at all times, except when switching from left to right lock and even this can be done within 1/2 a second. With no lurching, the revs will rarely climb much above tick-over, you will be varying the load with the clutch and matching it with the throttle. Simples!! Good luck

+1 on main bearings, good news is that theyre not expensive if a little long-winded to change, check the flywheel and crank pinion for "play" Dom

Hi I can only think of 2 ways that oil can come into contact with the coolant. Cyl head o-ring failure Water pump seal failure Truth is though, in most cases where there is a seal leak you lose the water to the oil, not oil to the water. This is due to the water being at higher pressure than the gearbox almost all of the time when hot. The most common indication of this issue is milky coloured gearbox oil. If it were a leaky cyl-head o-ring you would almost certainly be losing water gradually. This often coincides with a hard to start engine and overheating. Hmmmmm.... did you fill the coolant last... there isn't a chance some oil got into the radiator or hoses during a stripdown?? Dom

Coops When i first strarted on my gasgas i felt exactly the same. I could see others inching through off camber corners where i seemed to lurch into them, panicing, clutching, poor grip on the bars, making mistakes. I checked gearing, tickover speed... all the obvious things. In the end it was a combination of two things:- Fitting a flywheel weight to reduce the possibility of stalling. Practcing leaving the clutch slone and trusting the bike at low revs / tickover. Now i only clutch when i absolutely have to and approach hazards at much reduced pace. At the time, if asked i would have sworn it was the bike. Dom

although its a good question, pragmatism probably applies here. Make sure your bike silencer is in good condition . I'm guessing from your username its a Sherco 125 (2008?). Clearly, these don't have repackable silencers but you should be ok. I've got a 2007 125 that's well used but well cared for and its as quiet as anything else. Because trials isn't about power, speed, fashion, sustained high revs etc. very few people on modern 2T's meddle with silencers. Therefore I suspect that the sound testing will constitute looking for non standard / damaged silencers and then some testing based on "here, Bert..that sounds noisy!!" Happy to hear I'm wrong but I'd be surprised.

What do you mean "younger riders", They are younger riders!! As a novice I would concentrate on getting the basics right before worrying about hopping.

I came from Enduro which was reasonably friendly, but trials has been better still. We all know that we can be beaten by an older guy, wearing a flat cap and tweeds, riding a pre-65. Sort of brings you down to earth. Also, there's "relatively" little damage that you can do quickly lending out a trials bike. When I say "relatively" i'm comparing it to a 60mph crash on a KTM300 in the woods!! Dom

Dan No need for super unleaded, standard unleaded is fine. 70:1 / 80:1 is fine. as you guessed, 2T = 2 stroke, 4T = 4 stroke 4.5 = 450cc, 2.9 = 290cc Sherco market their bikes this way. Dom

Clav Apologies, this isn't a brief reply. If you replaced the base gasket that was already there (or one of a similar size) it's unlikely that the piston is touching the head (also, if it was touching you'd likely have destroyed the engine by now) Firstly,was the engine knocking before you rebuilt the top end? It's unusual for engines to fail instantly unless starved of lubrication. I would check the following in order of likelihood / ease of checking. Check everything you removed / adjusted / touched to ensure something isn't vibrating / loose / hitting something else. (this is my hunch) Check the plug to see if the motor has been running lean and detonating (also identified by hesitation when applying throttle sharply) Check that the motor returns to tick-over quickly and holds steady revs (crank seals) Check the crank bearing play on flywheel side by removing the flywheel side cover and try to move the flywheel up/down. Remove the clutch cover and do the same with the crank pinion. Check the squish (see below) Check the big-end bearing play (see below) If you've got to the "squish" on the list, this is checked as follows:- Select some soft solder approx 1.5mm dia and cut a straight piece around 6"-8" long (double up and twist to increase the diameter if necessary) Take the plug out Pre-bend the solder such that when threaded through the spark plug hole it will aim towards the cylinder wall (below the cyl head) Thread it through the plug hole and "feel" it touch on the cyl wall. Hold it there & get someone to bring the piston up to TDC using the kickstart Now apply steady increasing pressure with your foot onto the kick start (not a kick). When the solder has squashed (the motor will go past TDC) pull the solder out and measure the squashed end with a vernier or micrometer (the length of the squashed bit should be around 8-15mm long) If you haven't got a vernier / micrometer you'll have to use a steel rule and be very accurate. Bear in mind that the squish would have to be less than 0.3/4mm (125cc) and 0.6/7mm (290cc) to hit the cyl head at max revs. A good squish value depends on piston size but might be approx. 0.6-1.0mm (125) and 1.0-2.5mm (290). Engine builders change squish to achieve different performance characteristics or cope with different fuels. If in doubt go with the recommended value. If you've got to the "big end" bearing on the list, this is checked as follows:- Remove the cyl head and barrel Get the motor to TDC (most big-ends wear at TDC) Grasp the con-rod/piston with both hands and push up/down with the con rod EXACTLY vertical. ANY discernible vertical play is bad (only vertical play counts) You may have to rotate the crank 90 degrees at a time and repeat to ensure the wear isn't elsewhere on the crank-pin. Dom

Dany I'm similar in dimension to you and ride my sons 125 Sherco and my own gasgas 250 I find the 250 "easier" to ride simply because it requires less careful gear selection. Truth is they both have more potential than me. Given that trials bikes all have similar low seat heights / weights it really is about preference. Lastly, don't assume that large capacity = scary. Some manufacturers have mid capacity models that are "sharper" than their larger offerings. My advice, go to a practice or trial.. get talking to some people and borrow a short ride on some bikes. Dom

+1 to 0007's response. The condition you describe would be similar if you left the bike with the choke running from cold for too long. If your worried, take the bike for a healthy run and then check again. Make sure you put the motor under some load. Dom

struttf In the first instance i would have concerns of a different type. No frame number and no engine number are a very worrying combination. Worth a double and treble check that your looking in the right place (headstock for the frame and below the exhaust?? (from memory) for the engine number) Did the frame that you are replacing have a number?? Often your dealer will stamp a replacement frame and provide you a letter / certificate of some type. I have also seen the old frame headstock cut off and kept for proof of replacement. Its easy to over-react, but if there are no numbers there are few good reasons.

Glad there was a photo... i was checking it wasnt April 1st yet

Are you saying the pots appear have seized solid when you try to press them in by hand?? or when you use the lever / hydraulics to push them out in the normal way?? Its common for pistons to rock slightly, and jam, especially if they are a long way out of their bores. If i were you (and assuming the pistons still move with hydraulics), i would pump the pistons out quite a way and wet the sides of the pistons with brake fluid. The fluid will "wick" around the piston / bore area and wet the outer piston seal. I would then use a large screwdriver between some old pads (or similar thin flat material) to press the pistons back fully in as the previous post suggests. This way, the seals will be "lubricated" on the outer and inner edges and the pistons should move freely, however this is often a short term fix. Last point... as previously stated there is no substitute for removing the pistons completely and cleaning / lubricating the pistons; bore and seals. "Popping" the pistons out using the hydraulics or air is the normal way to do this. Some solvents cause the rubber seals to swell and increase the stiction on the pistons (sounds like this is the case), this will require replacement of the seals which are not expensive. If this has been a nightmare previously then i suggest the help of your local motorcycle mechanic. Dom

also, less tendency to stall. Can make the bike push on when you roll off the throttle though.

just re re-iterate some comments already made. Oils have moved a huge way since Castrol R was the vogue (30-40 years ago). I'm assuming that you're considering using it in a 4T. some reasons:- Have you ever had to strip and clean a motor run on Castrol R? It leaves a coating of varnish or gum on hot components; valves, exhaust headers; piston skirts;cyl-heads etc. Its a straight grade oil rather than a multi-grade (multi-viscocity) meaning it isnt as versatile temperature wise. However this is suitable for many classic engines. It comes from a time when de-coking an engine was common place. Modern semi and full synthetics are very low ash producing. Modern oils are lower smoke and lower odour. However, one plus is it's a very high load bearing oil. It took a while for synthetics to match this, but even cheaper oils are now there. Dom

tjay a boost bottle is a simple chamber that is connected to the intake port of the engine. So called because the chamber was often a small plastic "bottle" shaped item. The "bottle" was connected to the void between the carb and the reed valve. The idea was that atomised fuel/air mixture was drawn up into this chamber when the rider shuts off the throttle. The inertia of the intake charge fills the bottle and is released when the rider opens up again. Often found on 1980's Yamaha's as i believe they had a patent on the idea. See this diagram for clarity.. http://www.google.co...9QEwAw&dur=2698 2-stroke engine design has changed significantly since then.. Powervalves (not on trials bikes), improved carbs, reed valves, ignition, porting has rendered this design less necessary. Dom

Hi Press the "search" button and enter a shortened version of that question. Probably one of the most asked questions on trials central. Dom

Carl replating is around £130 + piston kit (£80??) from Langcourt replating. They use a number of agents all over the UK, so you may get it for less. Would i buy a bike with piston slap?.... it would make me worry about other high use issues (even when youve done all that work) trouble is that a 2003 200 pro isnt worth much more than £1000 if mint. sorry, not the answer you're looking for. Dom

Is it rattling..... Is it low on compression.... Is it down on power.... Have you got a big road / multi day trial coming up... No?.... then leave it alone Dom

This video is clearly aimed at observing expert / pro level riders and is relevant for national / world championship trials. 90% of club trials riders will simply stop moving forward or not. Much easier to see and observe. Whilst observing this level of riding skills needs explanation, It would be good to see a video that deals with the majority and helps the average volunteer observer. Failure to do this raises more questions than answers for joe average. Really, this is the same point as Jimmyl makes just expressed differently.