dombush

Thanks for the suggestions So, its currently running an S37, its blubbery on the transition and fuel screw was too rich until fully screwed in. Tried a U37 (because i had one) and the fuel screw was correct at around 1.5 turns out. Ever so slightly rich on transition Waiting for an s35 from splatshop (Chris told me that the relationship between S/U Dellorto pilot jets is.... S=U-3). hoping this is correct mixture at idle fuel screw 2 turns out and the transition is smooth and clean. I'll let you know (hoping for a package tomorrow) Dom

gradually getting my new purchase the way i like it. My 07 125 has a Dellorto VHST fitted and although it runs fine, the pilot and transition is quite rich. At a whisker above idle (1500-2500 revs) it loads up a bit. Also, the fuel screw can nearly be totally wound in to get the right idle mixture. So, the question is:- do 125's need an excessively rich pilot to help pickup... or is this just poorly jetted? It has a S37 pilot at present, what are other 125 riders using in their VHST's? Dom

Bondy given the very low stress and low temperatures that trials bike engines see, 40:1 is a tadge excessive, especially with modern oils. (i presume you use something semi or fully synthetic). The issue here is the ability of the plug to fire when under load (load = compression). Oil in the fuel is a good lubricant, but a poor fuel. If the extra oil is not being burned, it remains in the combustion chamber / exhaust and on the plug. Another point is that when you run 40:1 instead of 50:1 you are actualy running the engine weaker. Weak mixture + cold engine = poor starting. My advice is to change the plug (ensure it has the correct heat rating) and go back to a more normal ratio. Be aware that 50:1 is already "on the safe side" for a trials engine. Dom

Hi Ben There are some things you can do, but the danger will be making it peaky or losing what low-end it has. I suggest Fitting a correctly jetted Dellorto VHST, or a Keihin carb Refreshing the basic engine components (piston and rings or just rings) Reducing the piston to cyl head clearance (squish) by adjusting the thickness of the cylinder base gaskets. Cleaning the header and silencer sections of the exhaust system The header pipes on 125 Shercos feature a horribly stepped transition in diameter at the early part of the header. This causes carbon deposits ("coke") to build up around the transition. I "de-coke" this by heating the header with a blow torch allowing the oil in the carbon to burn away. The coke then just crumbles away. Do something similar with the aluminium midbox. A word of warning here, aluminium's melting point is much lower and therefore damaged easier. Also make sure you remove the o-rings first. Other methods i've used are just running the bike on the road for 20 mins (needs an insured, road registered bike) or using a hot air gun directly into the large opening of the silencer. [*]Gear it down to give yourself more usable gears when in section (i use 9-48). [*]Changing the reeds from the reed valve is a possibility, but i've found the reeds on recent model years to be as good as anything else. Dom

Copemech i read your profile and it says Texas, yet your replies sound every inch a Brit. Whats the truth? Dom

Hi Firecat As you indicate the C3 / C4 is the internal clearance of the bearing. This is needed because of the potential rapid differential temperature that can occur across the opposing "races" of the bearing during warm-up or if the engine sees significant sudden heavy load from a cool start. When this occurs the bearings skid on the races causing further heat, wear and ultimately a seized or failed bearing. While the dealer answer is clearly go with the intended C4 design, trials engines are low output and therefore dont generate large amounts of heat. Motocross or road race engines on the other hand can see rapid temperature rise due to the nature of the riding / track layout. They also have a specific output more than double that of a trials bike. So my guess (and it is a guess) is that you could get away with it. Personally i would ask myself if the extra cost is worth the risk though. Do you really want to risk splitting the cases again? This article explains it well..http://www.bikebearings.co.uk/crankshaft-gearbox-bearings/ Dom

Storminnorm Parts and tools you will need as well as a work schedule. Apologies if a little condescending:- Tools / consumables required containers for waste coolant and waste oil Allen keys, spanners, screwdrivers, pliers, rubber mallet (optional) Torque wrench and socket set. (8mm to 24mm) Clutch holding tool. (actually i improvised, but i wouldnt recommend this) Loctite 243 (optional) Centre punch, battery drill, drill bits, small punch Small hammer for rivetting (consider using a large punch as well) Dolly to rivett against (i used a large lump of steel) Grease (to lubricate o-rings, seals kickstart & brake pedal bearing etc.) Brake cleaner / degreasant Parts required Replacement light gearbox oil (450ml) Replacement coolant or antifreeze/water mix (get1 litre, actually a lot less) Clutch cover gasket Exhaust crush gasket Clutch basket, rivetts and cush rubbers Work schedule **********Allow 2 hours if experienced, 3- 4 hours if inexperienced******** Rear mudguard off, Turn fuel off, Disconnect fuel hose. Tank off Exhaust header pipe off (2 bolts at exhaust port). Can be left on, but easier if taken off. Drain gearbox oil by removing drain bolt. Loosen radiator cap. at headstock Prepare suitable fluid container, remove coolant drain screw and collect coolant Remove water pump cover (3 screws) and tie cover / hose out of the way Remove kick starter bolt and remove kick starter then clean shaft and splines. Check if brake pedal being pressed down would allow removal of clutch cover; (mine did) if not remove it. Remove all clutch cover screws, Remove clutch cover (may need a small tap with rubber mallet to break gasket line joint) jiggle cover off. Remove 6? clutch spring bolts and springs. Remove pressure plate, actuation components, thrust bearing (dont lose ball bearing in actuator collar). Leave clutch push-rod in situ. Reassemble all components and locate into removed pressure plate. Remove clutch plates and steel rings as a set (i tried to keep mine in same sequential order as a pack). Using a suitable clutch holding tool (splatshop sell one), hold the clutch stationary while removing the clutch hub nut. Remove the clutch hub, bolt, washer. Remove clutch basket. Note position and order of thrust washers and needle roller bearing. ********1/3 of the way through******** Follow Splatshop ring gear removal / reassembly & rivetting procedure. See blog section of splatshop website. ********2/3 of the way through******** Reassembly of the clutch / engine is the reverse of the dissasembly procedure. Consider degreasing and using some loctite 243 on the clutch hub nut (not strictly necessary but i did) Use the torques as specified in the pinned section of this forum. Refill gearbox with light gear oil (i used a 75w oil), Refill cooling system with antifreeze / water mix. Bleed air out of cooling system by kicking the engine over a couple of times with kill switch pressed.. Top up coolant and replace and tighten radiator cap. Make sure overflow hose remains clipped into top of radiator cap. ********Done********* probably forgotten things, but there it is. Dom

Copemech What made me plump for the clutch basket? Checked flatness and condition of all the plates, the hub and basket seemed round and true. The end plate was moving in/out... there isnt much else. i suspect that when i filed the clutch basket fingers i took slightly more material from the back end of the fingers (deeper notches at the back). This must have slightly tapered a couple of the clutch basket location fingers towards the closed position. This was only obvious with an engineers square after the event. I suspect that when the end plate moved out the plates didnt seperate because they were trying to slide "up a slope", hence the sticking. As has been said there is a step by step guide to rivetting a new basket to the old ring gear on the Splatshop website, follow the "blog" link. 2 hours work all in; Only "special tool" required is a suitably sized dolly to rivet against and perhaps a clutch hub holding device (i improvised).

In hindsight i have to agree with tony 27. After dissasembling the old basket / ring gear, rivetting the new basket together was quite easy. I fitted new "cush drive" rubbers at the same time and the whole lot including oil cost me around £50 After fitting, the bike (clutch) was much quieter, but the degree of progressiveness was a revelation. Previously the clutch was on or off within 5mm of lever movement. Now its probably 25mm of movement. Also, clutch "sticking" is a thing of the past & clutch drag is now almost non existent. So, my advice is as tony27 says.... the clutch basket should really be treated as a service item.

Thanks for your help guys New clutch basket, rivets and rubbers on their way I'll fettle the plates as described while its all apart Dom

The clutch on our recently purchased 07 125 is sticking. This mainly shows up as Stalling when put into gear even when hot Not allowing the bike to be freewheeled when clutch pulled in.(engine not running) Needing to pull the bike back and forth to free the clutch plates. Stalling the engine when coming to a stop. Cant kick start the bike in gear if stalled suddenly As soon as the clutch plates are "unstuck" they remain ok until the clutch is released and pulled in again. Whilst this rarely affects the bike whilst moving, it makes it hard for a 12 year old to manouvre the bike. Someone mentioned to me that heavily used 125's can suffer from warped clutch baskets / hubs. Does anyone know any more about this? Dom PS, i have alreadyt done some minimal filing of the clutch basket fingers to remove some fairly deep grooves.

Hi clearly your on the right track. Revs taking time / not settling down is weak running. A suggestion list:- Crank seal (done?) blocked idle jet (done?) air leak at crankcase halves (rare if the engine hasnt been splt recently) Air leak at reed valve manifold (either side of the manifold) Carb not seated well into intake rubber The most likely is the crank seal on the flywheel side (repaired already?). Common on Sherco's, this can happen on the clutch side also, but normaly is accompanied by smoke from burning gearbox oil. Blocked pilot jet or poorly adjusted idle screw (repaired already?). These can lead too poor starting / slow to return back to idle but the difference with your symptoms is the revving up without touching the throttle... this says air leak. A rare occurence is leaking crankcase halves (happened once to me). Usually caused by poorly fitted crankcase gasket during rebuild. Can sometimes be caused by a cracked crankcase due to an impact. So the list isnt too long, a couple of hours should see you in the know. Dom

Hi i too fitted an Ohlins shock to my 07 125 last weekend. During installation i noticed that the shock body and fittings were close to the frame and the airbox, but fitted in certain orientations. I ended up fitting the shock with the rebound adjuster at the top (albeit now not reachable when on the bike) and the lower body of the shock oriented so that the oil/gas fill screw faced towards the front of the bike. There were only millimeters to spare between the airbox and the shock body, the same between the shock body and the vertical frame tube that sits in front. I thought it was just me!! Still it does fit, if a little close. Dom

Hi Normaly grey oil is the result of general wearing of the clutch components, particularly the clutch basket fingers where these components are made from aluminium.. Its normal for this to occur after a number of hours running, so the question is... how much running were you doing between these oil changes? Other thoughts:- When you say the cluch packed in, this normaly means it is slipping. I've a feeling that you meant that it wouldnt disengage (stuck). If so, this is common if a bike has been left standing some time. Putting the bike in 3rd gear and rocking it back and forth with the clutch in normally frees it off. Again, not an unusual or particularly serious problem. If the oil hadnt been changed for a long long time, aluminium particles can saturate the oil and even settle out at the bottom of the gearbox. These "settled patches" then become resuspended into the new oil, this may be what you are seeing. Heavy use, a grabby and sticking clutch can be signs of notched clutch basket fingers. This is easily seen with the clutch cover off. If your a cheapskate like me, you carefully file the notches flat (it takes some skill / care to do this properly). So dont panic, other than spending more than you bargained for on oil, this may not be a significant problem at all. Dom

the good news is that Chris from splatshop tells me that its rideable whilst i save up for another!! Dom

Hi... removed the swingarm, shock and linkages today. All needle bearings are in a bad state and partialy seized but retreivable with some effort / money. More worryingly the lower "eye" and spring seat assembly on the olle rear shock is sitting at 5 degrees (or more) to the shock absorber shaft it is connected to. It looks like the seized nature of the bearings has tried to bend the shock rather than compress it. I have read that the thread between the shaft / lower "eye" assy can strip and be helicoiled. This is different but may be a variation. Has this happened to anyone else? Was it the shaft that bent or the thread in the eye assembly deformed? How do you dissasemble the shaft / lower "eye" assembly Its not obvious how to take the spring off the shock body? Will the shock need re-gassing etc when this joint is dissasembled? Any help is appreciated

Hi my guess would be a worn clutch basket. The grooves in the basket fingers mean that the clutch plates dont slide evenly when pressure is applied / released. A spot of minimalist draw filing is in order, trying to remove the same amount of material from each finger and keep the angle the same as standard. If the grooves are deep consider a new basket. Dom

Hi Been there, got exasperated....try this. Take a tie-down ratchet strap (wider 2" type is better) wrap it round the circumference of the tyre and tighten (a lot). This compresses the centre section of the tyre and flares the beads out. It also helps to use some tyre lubricant to ensure the bead seals as easily and quickly as possible. The pros use rubber tubes / piping that temporarily seals the gap between the bead and the rim. Good luck

Like a number of other contributors i neither witnessed this nor know the people involved. However a few thoughts... Like the speeding case mentioned, sometimes you get away with it, sometimes you dont. However if the risks of getting caught are high (e.g. losing a championship), then you act accordingly and behave whiter than white. Whatever the implications, if you ignore the rules then its just a matter of time. Its a shame for the rider, but like many sports at high level it takes a strong team effort to compete. If the team breaks down in one way or another then stronger teams will win. The one area that i do feel strongly about is dealing with such matters outside the press. With the loss of the championship and the publicity, penalties have been severe. Therefore it doesnt reflect well on either party to use the press to have a slagging match. Hopefully the governing body has stepped in and pointed this out. In my limited club experience i have witnessed significant gardening perhaps twice. Both times i ended up feeling sad that the individual needed to lower themselves to do it. At my level with almost nothing to gain from winning, perhaps the respect of your peers is the biggest reward. Gives us something to talk about though :-)

Nigel, i get the point you make... of course it would be better to not require it at all a few things. even though its only a 250, i'm small / light in stature I only get to ride once / twice a month and this is at events which tend to be "straight in" Confidence plays a large part in improvement, perhaps it can come off in a while either way, like wearing "lucky underpants" if it works for you...it works

1st trial report Pro's Definately cured me of clutch covering nervousness, especially when on a technical descent at low revs. Damped down some of my early section throttle snatchyness. No snatching smooths fork movements and therefore steering. Makes the bike feel more stable and predictable whilst "in section" Didnt break traction when first applying throttle on slippery climbs, allowing you time to react before the dreaded wheelspin starts. Con's lifting the front wheel over a log with fork bounce and a blip is less dramatic and needs a bit more work (no bad thing) losing revs after arriving at the top of a "full revs climb" required more judgement when to start reducing throttle. All in all, this has been beneficial for me, mostly because of my poor throttle control. Worth thinking about if you struggle in a similar way. Dom

Making the modification stems from not wanting to clutch so much, but rely on grip that the bike finds at very low revs (mud!!) I rode a beta evo and found that i trusted the bike immediately even when rolling on from virtually nothing. I then rode a 2010 250 pro (mines a 2006 250), it was much softer meaning that my hamfisted throttle control didnt upset the bike as much. I also lacked confidence in the bike not stalling at other times. Other options were to cover the clutch or turn the tickover up... both have their drawbacks. Well aware that its a personal thing... for instance i know that i i dont notice the snatchy pickup so much from the 3rd lap onwards. Probably because ive settled in a bit.

Wow, what a difference. So different that i initialy lost my balance just slow turning. Need to retune my body movements to match the new characteristics. All the lively snatchyness is gone, it'll pull you forward on tick over without that "teetering on the edge of stalling" feeling. I hope this reduces the my nervous clutch covering affliction. It remains to be seen if it adversly affects that effortless front wheel lift for getting over logs etc. Glad i had a dremmel, rattle gun and loctites available during fitting though.

Whilst not a specific answer to your question... ---can they ride already? (motocross etc,) ---are they quite lightweight? The reason i ask is that the ideal answer is a 125 from any of the main manufacturers. I suggest reading some of the reviews on T+MX or ask some of the riders at your local club. With a 125 they can learn and then ultimately compete on the same bike. Trials 125's are (compared to other bike sports)quite flexible in that they are relitively docile until you rev them hard. They are also not much heavier than the 50cc & 80cc options. My experience has been that its the first handful of rides that are telling. If they arent spooked by losing control a few times in the right environment, they will soon master the engine and you're away and can concentrate ramping up the degree of riding difficulty. However if they are complete beginners this may be a step too far as many youths start with an auto, onto geared 50's 80's. This leaves you with the option of buying an 80 or similar but expect them to grow out of it quickly. This is where the weight of the rider comes in. I could compete on my sons beta 80 (I'm 10 stone) except that the fork / shock springs are designed for a 4-6 stone rider. Lastly, there is a reasonably new GasGas 125cc 4 stroke model recently on the market. This is heavier but very controlable and would also have suspension suited to near adult weights. However, like the 80 you will ultimately end up changing this if they want to compete more seriously. Dom

That explains it... had visions of riders on TY250's I guess the engine is a derirative of the YZF250 lump with all the high-tech lightweight design that goes with it. Wonder how heavy that is compared to the more trials specific beta single cam engines. Dom