dombush

I'll measure mine in the morning. Dom

:icon_salut: anyway what we need to know is Paynts (my mind keeps reading that as something else) has solved his problem. Dom

The context was the bike revving up when the choke was applied when the engine was warm. Normally if the choke is applied when it isnt needed it will cause the engine to run very rich and therefore reduce revs. If the engine revs up instead its indicating something might be wrong. The basis of this is:- The choke plunger opens a seperate bypass air venturi that draws up extra fuel from the float bowl. If there isnt enough fuel to feed this circuit the engine will see the extra air without the fuel and will therefore behave as if there was an air leak (which technically there is). As with any other small air leak the engine will rev up and run slightly weak.

Hi itsafive If it were me i would probably check the simple and basic things first before spending much money. Check your oil mix ratio is something sensible (i use 80:1) Check if the engine cylinder (not clutch) rattles, especially at tickover. Check the compression, expect something near or over 150PSI after 5 kicks, throttle fully open. Take the exhaust header pipe off and inspect the piston for significant blow by (carbon below the rings) Clean the plug. Check the plug gap against spec Kick the bike over when warm and look for a strong spark with the plug earthed. Clean the carb Take all the jets and idle screw out and blast with an air line. Check the pilot jet isnt partialy blocked Check that the jets fitted are to spec. Set the float height Set the idle mixture screw Check the ignition timing is set to the standard marks. Check for splits / air gaps around the carb intake maniufold rubber. Look down the intake rubber with the carb off and look for broken / damaged reed petals. Dom

Credit goes to Chris at Splatshop for this:- http://www.splatshop.co.uk/blog/2013/01/paioli-ceriani-fork-oil-levels-for-sherco-trials-bikes-from-2006-to-2011/ Dom

hi If I were to guess it sounds like one of the following problems (as you suggest, all fuelling related):- Blocked pilot jet (doesn't explain the revving on choke when warm) Incorrect idle mixture screw setting as Ben says Fuel starvation, a variety of causes An air leak Normally a bike will run very rich if the choke is applied when the engine's warm, it will rev up if there's not enough fuel to match the extra air that the choke circuit provides. The only fact that intrigues me is that the bike seems to run ok when not asked to tick-over.. is this correct? If the bike also has trouble picking up as well but runs ok at medium / high revs I would suspect a blocked pilot jet. If the bike has trouble picking up and also runs very badly at other revs I suspect general fuel starvation / float height. If the bike picks-up ok and runs perfectly ok at other revs, I suspect the idle mixture screw. If the bike doesn't just die on tick-over, but revs up and down, I suspect an air leak. good luck Dom

OK, M7, that's the information needed. M7 metric coarse thread, 10.9 specification bolt (high tensile) = 21.3Nm recommended torque. Dom

Hi Sprinter 27 Not owning the 125 I don't know what size thread the Cyl Head bolts are, but I know that 22nm is a lot of torque if the thread size is not an M8 and/or very high spec material. See this link for suggested Beta torques.. be aware it refers to a 270. http://www.trialscentral.com/forums/topic/28936-torque-settings/ If you look up fastener torques on google like this:- http://www.leytonfasteners.co.uk/pdfs/TorqueValueGuide.pdf be aware there's lots of variables involved. Dom

Tony with the clutch mechanicals are as good as you state, the only other variables are clutch bleeding (not sure this would do this) and clutch plates. . First thing to ask... has the bike always been like this? or ist a recent issue? One issue is when not enough oil gets to the friction surfaces, this can cause overheating and grabbyness. Things to look out for:- Have the plates been replaced recently, are the grooves on the friction plates deep and clear of adhesive. Are the steel plates warped at all (often discoloured as well) When the clutch basket ring gear was fitted and rivetted, were the oil holes in the ring gear lined up with those in the basket? Lastly, ive heard good things about the dimpled plates offered by some manufacturers (again, these allow retained oil). thats all Dom

Hi My gasgas 250 (2006) is a snappy beast that i've tamed so it doesnt sound like the same basic bike. Things to check:- carb setup vs stock Hoofing flywheel weight fitted? Squish clearance (this makes a big difference) Ignition timing Exhaust condition. Reeds condition all the service type stuff (air filter, oil mix ratio, fuel) Dom

Tony you dont say what year or capacity the bike is?? Dom

Jason The coolant leakage and the "choked up" issues may or may not be linked. Right now my hunch is that they are probably not. Reason is that a bike will run normally (not under load) for a minute or so before overheating. Water leakage. Try to trace the source of the water leakage by working up from the point above the "puddle". Without belittling the problem it should be quite easy to spot the source as long as you use some anti-freeze that leaves a trace and doesn't evaporate. Unblocking of the exhaust I like the idea of running the bike very briefly without the rear silencer section, as although noisy it will prove the point. If you suspect the silencer section is blocked I suggest that you disassemble the silencer as follows:- Drill the heads off the pop-rivets that hold the end cap to the silencer body and punch the remains of the rivet into the silencer. Remove the end cap to reveal the silencer screen tube and the absorption material. Remove the absorption material from around the screen tube and then pull out the tube (it might pull out anyway) Note the orientation (radial and top end / bottom end) Inspect the screen tube for holes / collapsed sections / blockages etc. ********repair as necessary********* Replace the screen tube into the silencer Pack new silencer material around the "in position" tube using a long rod. Careful not to over compact the material. Replace the end cap ensuring the exposed screen tube locates into the and cap recess. Re-rivet the end cap in position using correctly sized large head aluminium pop-rivets. Materials costs are likely to be £5-£10 for the absorption material and £2-£3 for some large head aluminium rivets (assumes you have or can borrow a pop-rivet gun). Dom

Jason the most likely cause of a blocked exhaust is something blocking the bore of the silencer section. I don't want to jump at shadows but I would make sure that the silencer "mesh" hasn't collapsed and is blocking the gas path. This would cause increased back pressure, poor scavenging and therefore overheating of the piston, If your bike is a Pro model you need to remove the M6 bolt and 2 M5 screws that connect the silencer to the "centre" section. You can then look up the bore of the silencer and although its slightly kinked you should see daylight if all is well. Dom P.S. re cost of repairs..nothing discussed so far involves anything but your time to investigate.

Jason The fact that the piston has seize streaks in multiple radial positions tends to indicate that it is or is similar to a "4 corner seizure". Also two other symptoms also point at this. The ring land has melted / broken up in one place, and the piston crown has a grey/white colour.. this also points at the same issue. A multi point seizure is normally a sign of overheating of the piston which has caused the piston to expand more or faster than the barrel that surrounds it. This is usually caused by one of the following:- Over advanced ignition timing. Lack of engine cooling Blocked or restricted exhaust Overly lean jetting Extreme load placed on the engine from cold. So, I would check out these failure modes. Notice that some of these causes are similar to potential issues already identified before we knew this detail. I would check these first, especially the ignition timing, jetting of the carb (vs. standard) and blocked exhaust. Hope this helps Dom

Definitely possible to be done by the home mechanic... However, a well intended piece of advice is that if you don't have the necessary tools or know what you need to do, its probably a sign that you could do with a hand from an experienced pal or get it done somewhere. It takes me about an hour to strip the bike to get access and then take the barrel off. Apart from circlip pliers or hose-clip pliers there are few specialist tools needed, however if you want to measure the barrel and piston properly you'll need a bore gauge and a micrometer of the correct size. If you're confident that the barrel is worn out and are sure that you want to replate, I suggest the following:- Buy a piston prior to the replate, ensure it is of an A or B size so that you can go larger if you need to do so later. Send the piston along with the barrel (and the desired piston/bore clearance) to the replating company. This way you don't need to measure the barrel as the plating company will simply diamond hone the barrel to suit your specific piston. To save you getting any blank looks, a minor point is that the barrel is unlikely to be "chromed". Modern barrel plating is a patented elecro fusion process that has a numerous trade names, the most common of which is "Nikasil" Good Luck Dom

Mccarro ok, so at least you know.. The bore of the barrel is electrofusion (Nikasil plating) plated straight onto the aluminium barrel. Although very hard the Nikasil plating is only microns thick, so a score, scratch can easily render the barrel in need of a replate. Check if the barrel is beyond repair by checking if the damage is more than cosmetic. Although one would use a bore gauge for measuring general wear, a scratch or gouge is so "localised" that this isn't possible. The rule of thumb I use is that after cleaning off any residual piston aluminium if I can still feel a definite "step" with my fingernail its probably in need of repair. There are two types of repair. A diamond hone will deal with the scratch if its a micon or two deep, any more than this and your into a re-plate which costs around a 1/3rd of a new barrel. I cant tell where you live but I can say that the UK and US both have a couple of replating companies and these have a number of "agents" that can organise getting a new piston, sending off the barrel etc. I always buy a piston first and sent it with the barrel. This way i get the bore plated and honed exactly to suit my specific piston using the manufacturers specification for piston to bore clearance. Generally the replate companies offer a 1 or 2 week turnaround, then a small running in period will see you up and running again. Dom

Jason congratulations for one of the longest sentences ive seen recently First thing in diagnosis is... When / what went wrong when it was last working correctly (before you got it?) If this is reason is unconnected, it sounds very much like the following potential issues:- A carb problem, needing a thorough clean? Incorrect float height? Incorrect carb needle clip setting? Choke not fully turning off? Wrong petrol / oil mix ratio? Exhaust bunged up? Clutch side crank seal gone? Poor compression? Coolant leaking into the combustion chamber? (Cyl head o-rings?) Just a starter for 10.... first thing though is to find out why it was in bits in the first place. Dom

mccarro when you say the bike suddenly stopped, was it instantaneous like it locked up, or like it was starved of fuel due to being upside down? Like you guessed the float can stick open if it gets a real bang upside down, but this appears to be the opposite of your symptoms. My next steps would be:- Check youve got the same level of kickstart resistance you had before (compression) Check the throttle is returning properly with a "clack" when you let go of the throttle. Check there's fuel flowing to the carb by taking the fuel line off. Check theres fuel in the float bowl when you remove it (fuel on??). Clean the jets, especially the pilot jet. Check the float height is OK, in case you bent the float tang. Check the choke plunger is pulling up. Check you havent broken a reed by looking down the intake rubber with the carb off. this'll take an hour or so......but these are the obvious research steps. Dom

Ben M6x20 Dom

Ben, you mean i have to get off my backside and check again!! sigh!!

Ben My 07 125 (not sure theyll be any different to an 05) has M5x16's in all 3 instances. Just to be clear, I'm assuming that when you say the clutch cover you mean the smaller outer cover (4 fasteners) not the main RHS cover that has M6's holding it on. Apologies to Gasgas forum for the hijak. Andy will book a full fumigation and deep clean to remove all traces. Dom

Hoggy Just my opinion.. It all depends on what your doing. I assume that you intend to ride for hours at a time over some distance 40, 80 miles or more and intend to ride smoothly (being polite, as opposed to aggressively) then a light 4 stroke is best. not because you cant do it on other things, just whats easiest to live with. As an example of this I used to do quite a bit of laning on a KTM 300EXC (i raced as well) but it was annoying on the road due to the normal 2 stroke desire to be accelerating or decelerating. I tried KTM 200's and 250's they were similar, however i rode more road biased 2T machines (KDX220, DT125, CRM250 etc.) and these were better. On the 4 stroke front i preferred a 400 or 450 because they had similar power to the 2T-300 but were smoother and easier to deal with (also i found that four strokes spooked horses less) after the 3rd / 4th / 5th hour riding. A 250 4T is also good but it stresses the bike slightly more, 600's start to get a bit heavy for me (a shorty). Having said that i laned with a pal that used a KTM 990!! I stopped because i started to feel like an annoyance socially, racing was much more rewarding and also because i wanted to ride legally. Various factors mean that a SAT NAV and lots of route planning are advisable if you want to keep moving. Good luck, if all youve got is a 20 year old XT125... that'll do if your a good rider. Dom

magh I've had similar recently but the oil didn't turn clear again, this could just be related to the brand of oil or even the coolant. There's three possible sources of water seepage into the gearbox. Cyl head o-rings Water pump impeller seal Pressure washing in the wrong places. Undisturbed, the cyl head O-rings rarely fail, the water pump seal however does have a bit of history. I changed the milky oil in mine twice and ran the bike for 10 hours+ in between. During this the water level didn't drop enough to cause a problem. Fact is that the seal is reasonably cheap, is difficult to prove categorically and doesn't need any specialist tools so might be worth doing anyway. There's a good video on Jim Snell's Trials Parts USA website. Sometimes the seal wears a groove into the impeller shaft. Mine didn't need a new shaft, I just polished it up with some ultra fine Wet'n'dry. 3/4 hour job, worth doing if you suspect it. Job done Dom

Although I agree with many of the comments, can I suggest that we give it a few more trials to see how the riders and observers develop. If it continues as many think the rules will change, we may learn some good aspects to go with the negative ones.

Thanks guys, peace of mind restored