DeanG

Yeah, no more missfiring - My bike is chewing through clutch cables though lol - 2nd one just snapped and I've had it since....1st Jan this year Atm it just won't idle - But thats because the rectifier is bad - If I fully charge the battery it idles lol

For those who may read in the future, I found a loose earth on my rectifier - I will be replacing the bad rectifier very soon - But it is a temporary fix. Thanks for all your suggestions!

Yeah I rebuilt it myself - It has never idled since rebuild but the missfiring came recently I did recharge my battery the first time and it let it idle for about 10-15 seconds before dying I'll give the timing a once over though

Thats exactly what I wanna hear It does seem like a massive electric fault when it keeps missfiring like im hitting the kill switch, like the CDI is f*cked but it is most likely the rectifier Been quoted £57 for one brand new so I'll sort that out

Rebuilt my xt and ever since it hasn't idled properly... I've gone over the manifold a few times making sure there isn't an air leak with wd40 when its running (to no success) My rectifier is bad, so the battery doesnt charge so I have to keep charging the battery or its a complete bas**** to start :\ Anyway it won't idle, it runs with choke on (sounds like an air leak) and more recently it started missfiring at about 6k revs so I changed the plug and nothing changed - After 2 days the missfiring got really bad at any revs and began sounding like an F1 cars launch control/rev limiter lol Its unridable now it just missfires then dies I dont think it is an air leak because I can't find one but what else could it be? I'm thinking electrical

Ok got my piston today but I'm worried well... Told my mate who helped me get the engine out to take the piston off for me last week - Which he did but I never saw a small end bearing and he didn't put it in the tub? Came to reassemble today and couldn't find it - But its like it shouldn't be there... Theres the 2 circlips and the pin - where is the room for the small end? Or don't 4 strokes have small ends? never rebuilt one before (and no don't worry I know how to do timing so I won't be posting for help there lol) Cheers for all the help Edit: Oh by the way I got all my parts from a Yamaha dealer

Shops are for people who aren't in debt

Yeah pics do suck really bad sorry - Had to use a phone I can't find any batteries for my camera! Don't see much point getting new rings only, I'm not sure what it needs out of the 2 but I might as well replace the 6 year old piston if I'm doing the rings too! I can't even see any ring damage tbh I'm not sure at all... I was really confused by the scores, I can't think of an explanation to why they are horizontal, and they are all on the exhaust side with a few more faint scratches

Here's the pictures - Sorry I had to use a phone but I tried to make the marks as clear as I could - Doesn't help that I've cleaned the piston up a bit! http://up2go.us/static/img/IMG00859-20110123-1855.jpg http://up2go.us/static/img/IMG00860-20110123-1855.jpg http://up2go.us/static/img/IMG00861-20110123-1855.jpg Edit: Changed them to links they are far to big :|

Has it got compression - Or enough of it?

Air cooled

Oil levels were fine I checked them over a lot (Unless the previous owner neglected it for some time before sale - But when I got the bike it had enough oil still but I changed it anyway as a precaution) Bike just started smoking a lot once warmed up (Wouldn't smoke at idle, just on revs), sometimes it was white - then sometimes it was blue :| So I decided I'd strip it down and take a look - Found a few scratches on the exhaust side of the piston (which I am led to believe means a lean condition at some point) - But the funny thing is the scores are like 3 underneath each other going horizontally :S Around the sides of the piston there was a lot of evidence of burning of some sort - Which I thought wasn't normal. I was told the bike was reliable by a load of people - I mean its a 125 and a 4 stroke what more can you ask for lol - Bike never really did have much power at all but whether thats the fact that the bike never had power to start with is another thing... My 110cc pitbike pulled better anyway Thanks for all the feedback I'll get a picture of the scores tomorrow!

No scoring visible, feels smooth - The piston scoring isn't that bad at all either - Caught it at an early stage I want to check the stem seals too, but I haven't a clue how - No tutorials anywhere...

Must be the old one I got the sizes from - Looks like I'll have to go with the OEM one from the shop - Extortion but the only one I can find.. He wanted £34 for the piston £38 for the rings £1 for the clips and a few other bits - Came to £111 inc vat

Everything is stock, nothing has been altered and the oil was changed 3 weeks earlier to the correct type it said in the manual - Think it was just its time to go Yeah it is a chinease one, but really its only temporary as I don't have the funds at the minute (debt and what not) - So maybe a month or 2 with the chinease one then I was going to rebuild it with a genuine kit. Just need to know the size before I order - I think its 57mm Thanks for the reply

Hey, topend blew on my bike so I stripped it down today to find a scored up piston - Shop quoted me £110 for new piston, rings, clips etc but I've found them cheaper online... Is the standard (non oversize) piston 57.00mm? Cheers

Looks awesome! After a 2stroke though, and preferably a 250 Cheers mate

Haha it is quite small I'm 6ft 2 Don't know what bike to get next - Was thinking of a KTM 250 EXC but I kinda like the Yamaha scene - Are there any road legal enduro bikes out by Yamaha?

Hey I've already posted on the forum but I missed this section! I'm Dean from Manchester UK and I'm 17 currently in the progress of getting my test done! I have a Yamaha XT 125 R at the minute which isn't my favourite bike, but it'll do till I pass! Recently got my XT, beforehand I had a road legal pit bike which was really fun but... well it was chinease - but still fun because of its size! Only pic I have of my pitbike is whilst it was being built so there was a lot of bits hanging off: And heres one of me on my XT the day I got it: About to embark on a 2.5 hour trip from Birmingham to Manchester on a bike that does 65 flat out...... FUN

Sounds about right Gets me to work and back, and itll sort me out for my test I guess Until when I get myself a KTM 250 EXC

Yeah I see your point - I'm not really for making it faster I was just wondering why the hell it was there lol - Personally I don't see the point in making these bikes faster because I'm just using it to pass my test on, and then I'll sell it!

Everyone says the XT125 isn't restricted. I have a 2005 XT125 R and when I came to cleaning the air filter yesterday I found a big rubber cover over the top of the air filter with 2 small holes either side to let air through. Now tell me that isn't a restriction surely? I mean if I removed it, air will still be filtered - Just more of it... But then again that would mean a lean A:F so I'd have to rejet... Thoughts?

Ok thanks, had a bit of a bump in the ice - Think I've fractured my knee or something so I can't get into the garden to work on it... When I get a chance I'll check it over. Thanks for your help

Thanks for the reply Just tried it, nothing happened at all Started, pulled clutch in, put stand down and kicked it into gear. Bike carried on idling...

Hey, Hate joining a forum with a question - But I got my first Yamaha today (2005 XT125 R) as my first roadbike on CBT (sigh) Anyway, never seen this before but the electric start only works when the bike is in neutral... Is this normal? Even if I pull the clutch in it doesn't even try :S It kick starts fine with the clutch in, but its handy to be able to start in any gear in those embarrassing moments at the lights without trying to find neutral! Cheers