Munners

Finally! I am sooooooo pleased to report that the bike is now running like a dream. Thanks for all the advice along the way

Cheers Ian, excellent detailed advice thank you. I will certainly be careful not to make the same mistake again.

I believe I have found my problem. Convinced it is a top end problem I stripped the head off and following the latest advice from you guys I inspected the valves. Neither valve is seating properly with the exhaust valve being the worst. No need to do a leak test I can see clear daylight around 75% of it and fluid pours through. The intake valve is marginally better but again there is a small area where daylight can be seen through one side and again it doesn't hold any fluid. I considered stripping it down and replacing, but the cost of parts doesn't make sense over purchasing a complete new aftermarket top end which I have gone for. I will let you know how I get on Excuse the delay in responding to your advice but I don't have a garage and I am dependent on good weather to work on the bike and evaluate your suggestions to the problem. Cheers Jon

Hi all and thank you once again for your responses. Probably not necessary, but to make sure everything was as it should be I stripped the top end down, reassembled with new gaskets, checked and double checked the timing but still the flipping thing won't start. It doesn't even fire now (but I have a good spark) and to make things even more frustrating I now have no compression. It is absolutely zero! The only thing I haven't done is strip the valves down to check if there is a problem there. Once again I am looking for help and inspiration

Yes I did set the rings opposed using the diagram in the official workshop manual. However, to the question did I test the compression wet or dry is where my knowledge is limited. Not sure what that means but I just followed the Haynes guidance of attaching the gauge and cranking the engine over until the needle stopped moving up. In regards to there being two TDC's (I was not aware) although I thought I had pretty much followed the instructions to the letter I think it will be worth revisiting this aspect. Many thanks for your help so far

Hi all and thank you for the welcome. I have tested my compression tonight and I have a reading of 125psi. According to the Haynes manual it should have a minimum of 148psi but not sure this would prevent the engine from running

Hi all and apologies for the lack of introduction from a new subscriber A bit of background.. I am an unqualified but enthusiastic tinkerer of motorbikes and have done a couple of nut and Bolt rebuilds in the last few years (ST1100 & Intruder 125) with great success. My son has a YBR 125 (2011 fuel injection) which he ran with no oil and completely knackered the crankshaft. Long story short.... I dismantled (cleaned out all the metal filings) and rebuilt the engine replacing with new parts where required but now it won't run. I have replaced the crankshaft, piston and rings, checked and double checked my valve clearances whilst at TDC. I have a good spark, fuel is getting through and good compression. But when I try to start it, it fires but it won't run at all. The only problem I can find is the starter motor is noisy when I turn it over (replacement required) but now at a loss on what to look for. There are no fault codes showing so any suggestions would be very welcome.