dadof2

Obviously I don't know why you have suddenly had a problem. What I do know is that rim sizes and bead seating areas vary quite a bit when you would expect them to be constant. Also tyres vary both regarding bead diameter and the thickness of rubber over the cords in the bead area. Warming the tyre softens and expands it and the impact adhesive lubricates it so it slides into place on the rim. Without lubricant it can bind, stopping slightly short of fully seated. http://www.yokohamatire.com/tires_101/tire_care_and_safety/match_mounting/ See above link. Some manufactures use several more colours to match tyres to reduce the effects of manufacturing variations. I once had problems with a front tyre (tube type) that would seat and run true at 30 PSI but would not stay seated when pressure was reduced to trialling pressure. Method I suggest cured it.

Iridium plugs generally just have one earth electrode. It is their very fine centre electrode that gives them good firing properties. A few slow kicks with the throttle closed and kill button pressed cleans out the cylinder and helps starting. I am not familiar with the Sherco handbook, surprised they suggest a 3 earth electrode plug, these are usually used to give high mileage in cars, not easy starting.

https://www.youtube.com/watch?v=1EbXacjIV78 See above, I think your bike has this type of carb .http://danskkartingcenter.dk/dellorto_motorcycle_carburetor_tuning_guide.pdf See page 10 of above link From #5 I guess you are pretty new to working on carbs, may be best if you could find someone local who could work through your carb with you. You could easily make things worse, carbs are delicate

http://www.uk-motoplat.com/home.html Have a look at the above, might be able to help. I find hard to start 4 strokes tend to start best with just a shade more throttle than tickover. An iridium plug will help

Brings back happy memories. Would I be right in thinking Bultos of about this era have increased in price significantly over last year?

I quite fancy a 4rt as my next bike but whether I will actually buy one I don't know. Not bothered about competitiveness, just like a change from a 2t. I have had a Cub, C15 and TL125 and found them Ok to ride with no problem finding grip, but after many years or riding 2T trials I find the level of mechanical noise and less frequent firing intervals (at same RPM) disconcerting on a 4rt. Keep thinking it is about to stall or go wrong.

Suggest carb strip and clean paying particular attention to cold start enrichment mechanism and passages

Are you talking about hot or cold starting or with or without enrichment open?

The Dunlops are generally a tighter fit on the rim than a Mitchelin, that is why they don't come off so easy when flat or subject to side load. This tightness can stop them installing properly on the rim, meaning they leak intermittently when subject to flexing. These problems are more likely if tyre installed in cold weather. Keep tyre and rim in warm room for a few hours with tyre on rim but not seated nor inflated. Thoroughly coat rim and beads seating area with contact adhesive and immediately inflate to 45 PSI. Leave in warmth overnight.

Fine grey sludge like in your photo can be formed by old coolant dissolving the aluminium casings. I have seen this in coolant systems but not dispersed over the piston like in your photo. Coolant should be cloudy not clear, colour dependant on type. If it was clear someone has maybe put just water in.

Same sound problems on Terminator 2

Bit late for you unfortunately but I wonder if following suggestion may help prevent future theft from you or other forum members. Consider approaching your neighbours with a view to putting at least 2 CCTV systems up so the CCTV overlooks each other. By sharing the cost between say 15 households the CCTV costs next to nothing and is a major deterrent to all types of crime. I know several businesses who have adopted the above strategy.

Usual is about 0.1 to 0.12 mm per 25 mm of bore. I would expect the top ring to have slightly more gap than bottom ring as the top ring gets hotter and expands more

Total strip and everything fully cleaned and rinsed with 2t fuel / oil mix until no more dirt comes out. What coolant have you been using? and how old is it?

Best to push it in low gear to spin engine rather than excess use of kickstart. Make sure you earth the plug well also, otherwise the spark energy will go back into your ignition system and you will have more expensive problems to deal with.

The above suggestions will probably sort your problem but if they don't the check the spring loaded plunger on the float valve. It should move freely and smoothly any roughness at all can cause it to move irregularly causing intermittent flooding.

The Fantic frame is all steel tube. The Vertigo is steel tube in upper / headstock area then alloy for the swing arm / footrest area so I would say it is much more similar in design concept terms to the Benelli.

http://www.picoauto.com/jargon-buster.html Comes in handy at times, click on the letter the abbreviation starts with

http://www.kjm.net/usedbikedetail.php?id=27025 See above - is this where the Vertigo frame design came from. EFI & 4 Cylinder, note the price £4,599. Based on that Vertigo should be about £3,000

You can get bolt in valve with O rings, but if you can pull a rubber one in its better. Giver the hole a good polish with wire wool and make sure there are no burrs.

Agree to some extent, once the genie is out of the bottle it is very hard to get it back in. BUT something has to be done. Look at the WiTC 38 / 64 fails. Look also at http://www.trialscentral.com/component/attachments/download/1898 I can remember when we rode 90+kg tanks at this trial and in those days it had well over 100 entries and virtually no retirements. Something is wrong. I certainly do not attribute all the problems to light weight development but it certainly is a factor.

If you have a look at the CCMCC results I gave the link to you will see in second place was a twinshock, probably near 90kg. I do not want to make bikes heavier just for the sake of it, As I am the wrong side of 50 years old and carrying a few old injuries having a light easy to handle bike is preferable. What I feel would be to the overall benefit of the sport would be a restriction on development that adds costs and in some instances makes the bikes less reliable. At the moment to make their bikes competitive manufacturers have to make them as light as possible. A weight and exotic material restriction would end the necessity for manufacturers to develop in this direction, hopefully cutting their development costs and increasing reliability. I chose 77kg because that is about the weight of a ready to go 4RT. At some trials last year including a national I spoke to several riders who were able to flick their 4Rts about, some had been lightened, some were standard. Even F1 the costly pinnacle of motor sport has weight and development restrictions, but for some reason when it comes to trials, a predominantly amateur sport there are virtually no restrictions. Would Gas gas now be in a better position if it had not had to go to the expense of the lightweight pro engine development? Steve Earl states a 90Kg GG won;t get new riders into the sort, I can't disagree with that, but a more reliable lower cost bike would probably stop some quitting. When I bought my first trials bike it was not to compete in trials, it was to have something road legal that I could also mess about on on rough ground. I could also commute and go to the pub on it. Farmers used them for shepherding. That is how most people I know got into trials. That route for entry to the sport is now pretty well none existent and trials bike specialisation is a significant factor in this.

Try an Apico or Wiseco dealer. I am not sure what make the piston is in a sherco, quite likely a Vertex or Mahle. If you can find out may be able to get them through car engine rebuilder. Splatshop are a very good supplier, the high price of the ring is almost certainly not their fault. It is probably the structure and low volume of the trials spares market that is the problem. I can buy a set of 6 pistons complete with rings etc for a 4 litre engine, ie about £50 each yet a 125 cc piston for a trials bike is about £150

The Ohlins technician is both right and wrong. He is right in that a conventional Ohlins type shock cannot be valved to give rising rate. It does inherently have a very slight rising rate but nothing significant. A shock can be designed so the damping oil flow does give a rising rate on the compression stroke, but it cannot replicate the rebound characteristics of a linkage system and there are heat dissipation problems.

http://www.trialscentral.com/component/attachments/download/1883 Take a look at the above results. This is a club with a good history, good terrain (including Blaze fell that WTC is using) and a good number of events Serious lack of youngsters Quite a few oldies and a bunch of novices, no sign of progression through intermediate to expert. I know this is only one set of results but I chose it as it clearly demonstrates a problem. Unless something changes the sport will die or be greatly reduced and it won't just be Gasgas future in doubt. I know I will get slated from some quarters but the development route trials bikes have gone down is a cross between Pandora's box and a cul de sac. Whatever the reason be it low volume manufacture, exotic materials or high development costs, trials bikes are too expensive for what is a pretty basic single cylinder motorcycle. The FIM should announce dates on which exotic materials will be banned and increase the minimum weight limit by say 1 kg a year util it reaches 77 kg. To fit an expensive titanium exhaust to shave off a fraction of a kg and then have to cut costs elsewhere to compensate only results in things like poor quality bearings and unreliable ignition components being used.