geordabroad Posted August 24, 2009 Report Share Posted August 24, 2009 Hello I have a 2006 TXT Pro 300 that I've had about a year and never ride because I can't get it to start reliably. When I initially bought it, it started 2nd or 3rd kick every time. I took it out and 1 time (as I see often happens) it revved out Full open Throttle. I turned the petrol off to stop it as I couldn't think to do anything else (Never thought of using the choke). Since then I've replaced the worn slide in the carb (that caused it to stick open) and the woodruff key and got the bike going again occassionally, but never reliably. It seldom ever starts and the amount of kicking I have done seems to have had an adverse effect on the kick start mechanism, but that's not why I'm writing. As I said, after the full open throttle incident, I sorted the immediate issues out and ensured I got a spark and got the bike going. But if it stops I can never start it again. So, 1 year later I've taken the bull by the horns, dragged it's carcass up to my apartment and have it apart in my spare bedroom cum storeroom/ workshop. Head is off, as is barrel, to better allow me to check out the inside of the cylinder and the state of the piston, as I feel there was a loss of compression and suspected probable damage. Yes, the piston has some significant score marks in 3 places... 2 that are polished and probably 5mm each in width, and the 3rd area that you can physically feel the damage with your finger. The barrel has fared much the same with 1 area where you can feel the damage (not right to the top of the barrel) and this is mostly just above (2cm) and below (1cm) the exhaust outlet. My question is: a new piston and rings is around 130quid + VAT, a new barrel is 429+VAT (GasGasUK). If I only replace the piston and rings will it generally be OK? Or with this sort of damage is it necessary to replace the barrel as well? I'm not after a competition bike. I just want one with a decent engine that can blat around the hills reliably and be a bit of fun. I'm also going to get a head spacer to soften the engine and aid starting and will probably look at jetting, also in the hope of making it easier to start. Anyway, any input would be much appreciated. Thanks Ian Quote Link to comment Share on other sites More sharing options...
lee harris Posted August 24, 2009 Report Share Posted August 24, 2009 HelloI have a 2006 TXT Pro 300 that I've had about a year and never ride because I can't get it to start reliably. When I initially bought it, it started 2nd or 3rd kick every time. I took it out and 1 time (as I see often happens) it revved out Full open Throttle. I turned the petrol off to stop it as I couldn't think to do anything else (Never thought of using the choke). Since then I've replaced the worn slide in the carb (that caused it to stick open) and the woodruff key and got the bike going again occassionally, but never reliably. It seldom ever starts and the amount of kicking I have done seems to have had an adverse effect on the kick start mechanism, but that's not why I'm writing. As I said, after the full open throttle incident, I sorted the immediate issues out and ensured I got a spark and got the bike going. But if it stops I can never start it again. So, 1 year later I've taken the bull by the horns, dragged it's carcass up to my apartment and have it apart in my spare bedroom cum storeroom/ workshop. Head is off, as is barrel, to better allow me to check out the inside of the cylinder and the state of the piston, as I feel there was a loss of compression and suspected probable damage. Yes, the piston has some significant score marks in 3 places... 2 that are polished and probably 5mm each in width, and the 3rd area that you can physically feel the damage with your finger. The barrel has fared much the same with 1 area where you can feel the damage (not right to the top of the barrel) and this is mostly just above (2cm) and below (1cm) the exhaust outlet. My question is: a new piston and rings is around 130quid + VAT, a new barrel is 429+VAT (GasGasUK). If I only replace the piston and rings will it generally be OK? Or with this sort of damage is it necessary to replace the barrel as well? I'm not after a competition bike. I just want one with a decent engine that can blat around the hills reliably and be a bit of fun. I'm also going to get a head spacer to soften the engine and aid starting and will probably look at jetting, also in the hope of making it easier to start. Anyway, any input would be much appreciated. Thanks Ian A new piston and rings yes, but not a new barrel. It can be re-plated to match your new piston and I would recommend this. Cost is about 180 quid (http://www.langcourt.com/index.htm) If you are real unlucky, the crank and mains may need doing also..... Quote Link to comment Share on other sites More sharing options...
5again Posted August 24, 2009 Report Share Posted August 24, 2009 GG UK also do an exchange barrel + piston service, maybe more up your street, used to be around Quote Link to comment Share on other sites More sharing options...
jse Posted August 24, 2009 Report Share Posted August 24, 2009 A new piston and rings yes, but not a new barrel. It can be re-plated to match your new piston and I would recommend this. Cost is about 180 quid (http://www.langcourt.com/index.htm)If you are real unlucky, the crank and mains may need doing also..... Usually the only thing that wears on a cylinder is the bore plating, so an exchange is the best bet. Before you put everything together, you might do some serious "failure analysis" (an unfortunate, but necessary proceedure from my old dragracing days....) and find the cause of the unusual wear that produced your symptoms. Look carefully in the bell of the carb and the intake boot and if you have deposits of fine grit, the air filter and/or airbox is causing dirt to enter the cylinder. I would always advise that you should never "fix" anything until you have determined the cause of the failure. As the Pro engine has the main bearings lubed by the gearbox fluid, grit will not usually cause them problems (provided the engine has had regular maintenance) but you might look carefully at the rod big-end for ANY straight up/down clearance (wobble and side-to-side clearance is not unusual). You might also measure the ring end-gap as that will be a direct indication of the amount of wear. Standard assembly tolerance is to have 0.1mm per inch of bore diameter, so you can compare what you find to what the ring started at. Jon Quote Link to comment Share on other sites More sharing options...
uhoh7 Posted August 25, 2009 Report Share Posted August 25, 2009 I just replated my 300 pro at langcourt USA, sent them an oversise wossner piston and they matched it . about 180.00 US + piston 175.00 US. You will need o-rings and base gasket. Your previous starting issues may have been jetting. I would be sure to get a selection of mains and pilots for the delorto. This fixed my bike--it always starts. GG usa has video on kickstarting properly--to aviod damage. I guess alot of people don't do it right. Quote Link to comment Share on other sites More sharing options...
geordabroad Posted August 25, 2009 Author Report Share Posted August 25, 2009 Thanks everyone, still not sure whether to just get a new piston (very easy) or exchange the barrel (difficult)- I checked with GasGas and they still do this and have one in stock. The wear is pretty minimal so I think in the first instance I'll get new piston and rings, jets etc. etc. and see if I can get the bike going reliably. I don't feel the barrel will cause too much of a problem, it is not more than just the surface of the coating of the inner sleeve, so I think it should be OK, and shouldn't really cause too much of a compression problem for starting (I hope). Not sure about future wear though, as the main portion is both sides of the exhaust outlet . Will this pattern of wear repeat itself or do you think it is the result of full open throttle without petrol? If you have misgivings with my amateur diagnosis, please voice concerns and I'll reconsider It's a pain in the ... sorting this out from Beijing so a new piston is also the easiest, rather than rely on friends and colleagues to drop off, pick up new cylinders when they're in the UK! Cheers Ian Quote Link to comment Share on other sites More sharing options...
dschigoda Posted August 25, 2009 Report Share Posted August 25, 2009 ...Not sure about future wear though, as the main portion is both sides of the exhaust outlet . Will this pattern of wear repeat itself or do you think it is the result of full open throttle without petrol? ...Ian A cylinder will always have more wear in the front, due to the forces and motion of the piston and crankshaft during the "power stroke". In other words, the crank and connecting rod exerts a force to the front of the liner as an outcome of taking the downward pressure from the piston. Dave Quote Link to comment Share on other sites More sharing options...
uhoh7 Posted August 25, 2009 Report Share Posted August 25, 2009 get serious with your jetting, and watch the radiator overflow carefully--as soon as it starts blowing, stop the bike and let it cool. Never ride without checking your water level. Quote Link to comment Share on other sites More sharing options...
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