jon v8 Posted January 1, 2008 Report Share Posted January 1, 2008 Happy new year to you all,hope its a good one ! Having a couple of issues with my sons "new" Ty80, the main one being that it feels like the throttle is sticking open after reasonably large throttle openings when the engine gets up to temp.I've proved that the throttle isnt actually sticking.It has a brand new,freshly oiled venhill cable and I fitted a really strong return spring as an experiment.When the engine carries on revving you can close the throttle completely then when you start to open it again you can feel it pulling the slide open right from the bottom.This leads me to think it must be pulling in air elsewhere,perhaps around the reed block,main seals etc.Anyone seen this before ? It is also has more top end noise than I'd like and I wondered if anyone has any opinions on the quality of the aftermarket piston kits or should I spend the extra and go genuine.Cheers Jon. Quote Link to comment Share on other sites More sharing options...
baldilocks Posted January 1, 2008 Report Share Posted January 1, 2008 Try the coupling at the front of the carb as even when tight I could still move the carb on my sons TY80. If not ignition side crank seal ? Quote Link to comment Share on other sites More sharing options...
andy.t Posted January 2, 2008 Report Share Posted January 2, 2008 (edited) jon v8,that sounds strange,could it be one of the air passage ways blocked in the carb and causing a venturi action like on the old SU carbs. Edited January 2, 2008 by Andy.T Quote Link to comment Share on other sites More sharing options...
kevin j Posted January 4, 2008 Report Share Posted January 4, 2008 does sound like an air leak somewhere. tips I got from this board: 1. while running, run water across the assorted joints of the engine. Sucking in minute quantiy of water will seal the air leak briefly and engine sound will change. 2. spray with wd40,same effect but messy 3. Use small butane/propane torch UNLIT to apply butane various places. If it sucks in the fuel gas, it changes engine sound. (butnot in the electricl area with points making sparks!) I have done all three and they work. Sounds like you have verified the slide is working right, butr FWIW for others: TY80 carb has a small brass index pin in carb body that keeps the slide aligned right. That pin tends to work partially out, causes slide to hang up at part stroke or just off idle or full stroke. Push it back in and dab some epoxy on the outside of the carb body at the small boss where the pin is pressed in. kcj Quote Link to comment Share on other sites More sharing options...
jon v8 Posted January 4, 2008 Author Report Share Posted January 4, 2008 Thanks for the replies,I'll hopefully get a chance to look at it this weekend - does seem a strange fault,I did blow out the pilot and mainjet with the airline,but I ignored the cold start jet and plunger because it felt so much like the slide sticking.Trouble is I am limited with time,and as you all know when an issue goes past all the obvious simple things you need to sit down and think about it,then look more closely.I'll post what I find. Quote Link to comment Share on other sites More sharing options...
jon v8 Posted January 5, 2008 Author Report Share Posted January 5, 2008 Had the cold start jet apart,all OK.So I took off the flywheel cover - the mains are shot,Bu---er ! I reckon thats where the air must be coming in from.Thats the only trouble with buying a bike just from photos,but in a way I dont mind because I can strip it,go right through it and it should last ages.So does anyone have any preferences on OE or pattern piston kits ? Quote Link to comment Share on other sites More sharing options...
andy.t Posted January 5, 2008 Report Share Posted January 5, 2008 jon v8,glad you found a fault,would the shot mains cause what you mentioned(When the engine carries on revving you can close the throttle completely then when you start to open it again you can feel it pulling the slide open right from the bottom.This leads me to think it must be pulling in air elsewhere)The slide getting pulled open bit,i thought the shot mains just let air or oil in,or both,just curious how this cause the slide to lift,anyone know?. With regards to the piston I fitted a MATIKA piston on my 175 as there were no originals available,you may not have much choice. Regards Andy.T Quote Link to comment Share on other sites More sharing options...
jon v8 Posted January 5, 2008 Author Report Share Posted January 5, 2008 Sorry Andy,should have made it more clear.When its revving without opening the throttle you can feel that the twistgrip is pulling the slide up from its fully closed position because of the strength of the heavy spring I fitted to test it.Hence looking for air getting in elsewhere - I didnt mean that the extra air was lifting the slide,just that the engine wouldnt shut down. JK Hirst list both genuine and pattern pistons,and when I built my TY250 twinshock last year I was disappointed how noisey the top end was.I could only get a pattern piston for it and it was VERY carefully put together.If there is any doubt I'd rather spend the extra and enjoy a decent,longlasting motor.Not that I blame Hirst's at all - they are very good,really helpful. Quote Link to comment Share on other sites More sharing options...
andy.t Posted January 5, 2008 Report Share Posted January 5, 2008 jon v8,probably just me being a bit thick with regards to the throttle slide.With regards to the pistons although I did try to get an original for my bike I did have thoughts on whether the new modern pistons should infact be better than say the originals,you would think they should be with modern manufacturing process.I think alot has to be said for the guy who does the rebore. Regards Andy.T Quote Link to comment Share on other sites More sharing options...
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