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hey everyone, well here's the update. it's costing a fair bit but i want it back on the road.... it needs: piston kit rocker arm exhaust valve spring seat valve collets head gasket LABOUR!! should have the bike back on the road by the end of next week. the guy said that the collets had broken damaging the spring seat and therefore forcing the valve onto the adjustment screw. so overall verdict: exhaust valve knackered = no compression = no vrooooom vroooom

yeah, does seem funny looking back on it but then that's what these forums are for. to help diagnose things and help one another, right? thanks blackhat, although i never even saw your post!

finally hit the nail on the head, thanks OG The collet was damaged as you can see from the pic. Roy from the bike shop(RP Motorsports) has literally just come and taken the bike away. I had everything exposed so he could instantly see the problem. also pointed out how freely the valve moved from side to side. he said this was why the bike would have cut out in the first place, no compression, and of course why it won't start! i'll hear back later on today from him with a full and final verdict. will let everyone know as i know in my experience it's always nice to know what the problem was and how it was solved for other people's sake. thanks so much for everyone's support and guidance

i haven't had time to check this but i'm going to do it tomorrow. i've provide a pic with stages broken down as follows. this is as best as i can describe what's happening, so please bear with me: 1. loosen 2. turn anti-clockwise 3. bottom of screw moves up 4. top of spring also moves up there is never any clearance. i can turn that screw all the way up and the top of the spring will sit against the rocker arm. if i carry out the same principle on the intake valve i will get a gap/clearance and the top of its spring does not move

the manual said to get to TDC and align the mark on the cam sprocket with the alignment stud at the top, which i had already done

i've unscrewed it all the way and the valve just follows it up...it's now high enough so the rocker arm rubs on it. there is no clearance, you can't fit the smallest feeler gauge in between the screw and valve

no, its not stuck it moves down then up as i turn the motor. if you watch both the valves as i turn the motor, you can see the intake valve move down then up, then shortly after the exhaust valve does the same.

i thought the same and turned it to next TDC but no difference. infact i checked the clearance at several stages of the valve stroke but it stayed the same. the intake valve was a doddle to adjust and when i loosened the 10mm bolt i could turn the adjustment screw easily with my fingers. this wasn't the same for the exhaust valve, i had to turn it with pliers but every time i did the valve followed the screw up if that makes sense

hey everyone. took the valve covers off and camshaft cover off this morning and this is what i found: 1. took the camshaft cover off and it looks as if the timing chain had been rubbing on the inside somehow 2. looking at the exhaust valve, the screw was damaged/cracked. it was sat very tightly against the valve tip so i tried adjusting it but the valve kept moving up with the screw and there was never any clearance i also noticed the top of the exhaust valve cover had a little indent inside it which is where i think the top of the screw had been hitting it i made sure the piston was at TDC before i touched the valves. i could also see both valves move down and up so there's no issue there. apologies on the size of pics

Right ok, will have a looksee tomorrow as I'm checking the valves. Will do the compression test beforehand though. Hoping to get the bike back running by Friday as it's back to work then

Not got a compression tester but heard of that thumb over the plug hole test. There's no kickstart so I'd have to use the electric start assuming that's safe enough? I've had a look through that manual, checking the valves and adjusting them seems fairly easy so will give that a go tomorrow. Wish I had a garage I'd be on it now and all night

thinking about it now, that sound is probably the valves and they need adjusting. could be wrong though?

yes was when i let out the clutch. i didn't open the throttle and the spark plug was in

here's another video for everyone, it shows what happens when i try to bump start my bike....you can hear that "clicking" and it does sound very much like it's coming from around the engine area. it may just be i wasn't going fast enough. see what everyone thinks My link

I've got the correct plug, double checked from that manual and it is the right year for my bike. i measured the secondary with the cap off

not too sure on the diode but it was in the manual to test it but to be honest, I don't think that makes too much of a difference. i've just taken the spark plug cap off, measured the resistance and comes out at 4.90....upon looking closely at the plu it says its only a 5k resistor cap and it should be a 10k so i'll definitely be ordering a new one along with the ignition coil. i wonder why a 5k was on there in the first place coil is on wemoto but struggling to find the cap anywhere at the moment....

had a look into this too, checked the spark plug after cranking it a few times and it was completely dry so i guess you were right, no fuel. So, stuck a clear tube on the overflow pipe and did the float check....it was far too low! so took carb off and cleaned it up(again) paying particular attention to the pilot jet and adjusted the float. fitted carb back and cranked it again, spark plug still dry. so i tried putting a little fuel into the plug hole but that did nothing

ok so i followed the manual to the letter to do the resistance tests. did continuity tests on the switches too. these are my results: 1. Spark plug cap, it wasn't completely clear where I should be putting the -ve probe so I went to ground on the ignition coil and got 7.83, should be 10k but may have tested this incorrectly 2. Ignition coil primary resistance 0.06, should be 0.18-0.28 Ignition coil secondary resistance 7.83 3. Pickup coil 775, should be between 656-984 4. Source coil 778, should be between 624-936 5. Diode continuity, there was continuity both ways 6. Main, engine stop, start, sidestand and neutral switches all have continuity So, looking at this I would assume I need to replace the ignition coil and perhaps the spark plug cap(depending on whether the test was correct?)

right ok, i will check properly tomorrow then. i think because of all the frustration not knowing what was going on i've obviously made a mistake on the readings here. thanks for that though, hugely appreciated and apologies if you feel you're time has been wasted

oh.....well don't i feel stupid. still though, that secondary test still showed 0.00 on the multimeter and it suggests if any of them are incorrect the coil should be replaced

oh, this is the one I thought you had: http://www.scribd.com/doc/27325375/Yamaha-TW-125-Service-Manual-1999 same site though

p. 241

yes this is my 2nd....the first one got stolen after only owning it for 2 weeks

that's the manual i've been using Between ignition coil and plug cap it was 6.76ohms which is normal according to the manual. But between coil and earth it read 0.00 and supposed to be between 0.18-0.28 and it suggests to change the ignition coil if any resistance is out. My multimeter shows .1 on the screen before I carry out a test incase anyone wondered.

fuses are fine. i've had the carb off, cleaned it. also checked filter and cleaned that too. the old spark plug was wet when i checked it and i was told this was due to over-fuelling or the engine was flooded. so i took the plug out to let any fuel in there evaporate. fitted new spark plug and did the test, although the spark did seem rather weak to me i fitted it anyway and removed it to check if it was wet but it was dry. the only thing i can think of now is perhaps the ignition coil has gone?