alan_nc Posted February 24, 2010 Report Share Posted February 24, 2010 This is my plug after one section this past Sunday (and yes I cleared that one). Sorry about the picture - it's hard to get a close up picture, should have used a tripod. The bike is a TY250A, running 110 octane leaded gas, Bel Ray Synthetic mix oil. Any idea what caused this and second how can I avoid it in the future. By the way, I probably have at least 100 hours on this bike with no problems. Changed the plug and it fired up first kick. Thanks in advance. Alan Quote Link to comment Share on other sites More sharing options...
tonybroad Posted February 24, 2010 Report Share Posted February 24, 2010 how long had the plug been in the bike before that happened and have you run 110 octane and the bel ray before can you get a better picture, plugs can whisker up for a variety of reasons from over-fuelling which is usually easy to rectify to metallic pick up which can be more serious - is the whisker just carbon or are there metallic particles in it, might have a better idea good luck Tony Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 24, 2010 Report Share Posted February 24, 2010 Alan if you change fuels it can cause any existing carbon to come free and it can bridge the plug gap. When we stopped selling leaded car fuel here in Australia it forced almost everyone to using unleaded for their lawnmowers, outboard motors, motorbikes etc and there was an epidemic of fouled plugs that went for a few years - as old carbon deposits came off. If your bridge was carbon you will probably get a few more bridges then it will be fine as the loose carbon will have gone. If it is a metallic looking whisker then it is probably that leaded fuel you are using growing conductive crystals (too rich and/or too cold a heat range spark plug for the concentration of metals in the fuel). Quote Link to comment Share on other sites More sharing options...
alan_nc Posted February 25, 2010 Author Report Share Posted February 25, 2010 Have been using the 110 octane leaded (it's allowed as racing fuel only here, not sold as pump gas) for over a year in the bike. Have also used Bell Ray full synthetic for over a year. Plug is a NGK b5es, it had been in the bike for probably two trials, gap set at 21. The "whisker" is definitely carbon. Alan Quote Link to comment Share on other sites More sharing options...
copemech Posted February 25, 2010 Report Share Posted February 25, 2010 I don't know why you need 110 leaded in the first place. Acyually it does not burn well in a motor that does not requier it, then add the potential TEL residues. You might ck the deposits on your piston and head as well. Quote Link to comment Share on other sites More sharing options...
1oldbanjo Posted February 25, 2010 Report Share Posted February 25, 2010 (edited) I second the vote for not needing 110 Octane, and agree that the bike would probably run better on pump gas. If you are using this fuel to avoid ethanol blends in pump gas - I am going to switch over to VP SEF 94 fuel. It is 94 Octane and it will not deteriorate like ethanol pump gas. Edited February 25, 2010 by 1oldbanjo Quote Link to comment Share on other sites More sharing options...
alan_nc Posted February 25, 2010 Author Report Share Posted February 25, 2010 Guys, Well I do hope the gas isn't the issue on the plug. Here is my reasoning on 110 octane leaded gas. The bikes were built/designed to run on leaded gas (110 octane is the only leaded I can buy). Leaded gas runs cooler as does higher octane gas. With the speeds we run (lack of air flow cooling) I felt that anything I could do to make the bike run cooler was a plus. Alan Quote Link to comment Share on other sites More sharing options...
ducman Posted February 25, 2010 Report Share Posted February 25, 2010 You need a NGK B7 ES,that is the right plug not a 5 ES. Chrs:Mike Quote Link to comment Share on other sites More sharing options...
tony283 Posted February 25, 2010 Report Share Posted February 25, 2010 Alan, As Mike said the correct plug for this model is B7ES and for your TY175 it should be the B9ES. With regard to the fuel these machines were originally running on 20:1 (ish)using fairly low grade leaded. Currently any good oil with premium pump fuel is acceptable at 40:1 and like any 2 Stroke of the period you can expect plug fouling once in a while as David suggests. Our modern day fuel does not much care for oil and will need to be changed about every 2 months if you are still using the same mix from a can as it will leave a tacky varnish like resin on piston, rings, reeds, carb slide and in the petcock. I always carry a spare plug on EVERY outing as I have done since I started in 1962 ! I doubt you could ever overheat the Ty250A motor and when I had the FIRST one imported to the UK for the 1974 SSDT the Yamaha mechanics advised dropping the choke on the long road sections and ride through the burble and spits. These bikes would do over 80 mph on the public highway !!! not bad with 4lbs in the rear. Tony 1 Quote Link to comment Share on other sites More sharing options...
johnnyjazz Posted December 19, 2017 Report Share Posted December 19, 2017 sorry to revive an old thread...hope thats ok! but 80 mph!! really?? you kiddin?....im lucky to get 40-45 out of mine, tops!!! (w/14-53) though interesting you talk of the choke as an 'enrichment valve'. does that really work like a booster switch or something at high speeds? i'm curious also when you say you could never overheat the ty250a motor...can you rev the absolute beejezus out of the thing? im just worried about blowing the engine in case i got the pre mix wrong!...(.im at about 45.1....) thanks for any advice, johnny Quote Link to comment Share on other sites More sharing options...
shakennstirred Posted December 19, 2017 Report Share Posted December 19, 2017 I would have thought 110 octane is to high, unless you also change the advance of the ignition, as it burns different from regular gas. 1 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted December 20, 2017 Report Share Posted December 20, 2017 On 20/12/2017 at 7:28 AM, johnnyjazz said: sorry to revive an old thread...hope thats ok! but 80 mph!! really?? you kiddin?....im lucky to get 40-45 out of mine, tops!!! (w/14-53) though interesting you talk of the choke as an 'enrichment valve'. does that really work like a booster switch or something at high speeds? i'm curious also when you say you could never overheat the ty250a motor...can you rev the absolute beejezus out of the thing? im just worried about blowing the engine in case i got the pre mix wrong!...(.im at about 45.1....) thanks for any advice, johnny Using the start lever "enrichment valve" is sometimes used to cool the motor when it is being hammered along at full or near full throttle. Yes the extra frictional heat generated by the rings from riding at constantly high RPM can cause problems. Two strokes are very sensitive to jetting when used at consistently high output, which is why it so tricky to get a road racing two stroke to run properly, and not seize when you back off the throttle at the end of a long straight. If you are going to ride your TY250 along a freeway at 60 MPH, correct jetting is way more important than if it is used for trials or trail riding, or low speed road use. Problems can be minimised by gearing the bike to suit the speed you want to ride at. For general road use a TY250 should have at least 16/53 gearing. 1 Quote Link to comment Share on other sites More sharing options...
johnnyjazz Posted December 21, 2017 Report Share Posted December 21, 2017 (edited) wowsers guys, you are all the best! coming here is like going to school for me so thank you senor feetupfun, thank you always for such valuable chunks of knowledge and experience. i totally understand now how the choke would help cool the engine by letting in more air. however, after much trial and error, at your recommendation i stuck with the original 12/53 gearing and just working on super slow stuff. trials all the way! i have the carby set to all the correct specs as are in my manual, 114 main, clip position 4 etc. she's running a beaut now after replacing that o-ring, i feel so lucky and pleased to have her in my care for a while. Trials is so great and just as in music, the slowest stuff is the hardest and most challenging. im utterly rubbish mind you, but getting better in the empty parking lots and industrial estates around Brooklyn! the cops haven't been best pleased at times, but having it all street legal w/ insurance etc really helps. but wow, good to know potentially with right jetting and gearing a ty250 motor could do 80mph and one question, hypothetically, if i were to be riding on a highway at 60mph what size main jet would i need? bigger yeah to let more fuel through? and presumably at higher speeds 40/1 is a much better choice than 50/1 pre mix? not that i'd run her like that, but great to know just in case... really inspired to be learning so much about something new. thanks again to all. best wishes, johnny Edited December 21, 2017 by johnnyjazz sp Quote Link to comment Share on other sites More sharing options...
tony27 Posted December 21, 2017 Report Share Posted December 21, 2017 Using the choke lets in more fuel rather than air, more fuel cools the piston, more air leans out the mixture which creates heat. This is why air leaks are a major problem with highly tuned motors It sounds wrong but more oil means larger jets are needed as every extra oil molecule means 1 less fuel molecule getting to the motor 3 Quote Link to comment Share on other sites More sharing options...
johnnyjazz Posted December 21, 2017 Report Share Posted December 21, 2017 ah! yes of course thanks tony...choke = more fuel not air. my bad. and does that mean if the manual says a #114 main jet when the bike ran the oil pump from new then premix would require like what a 116 or 118 jet or something? this is all new to me jetting and stuff... but exciting. thanks so much for your help and input Quote Link to comment Share on other sites More sharing options...
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