atocp

Ok, so i think I've found the problem. Turns out the head gasket wasn't sealing properly because one of the cylinder rods wasn't tight enough. Looks like I've ripped out the threads on the engine block where the rod screws in. I'll add some Super Steel epoxy weld to it and hope that the rod can stay in tight, and report back as to the success of it. I'm hoping this works. cheers, atocp

Hi all, Wondering if anyone had any ideas as to what might be going wrong here. I cleaned out and set the carburetor of my yb100 and put it back in. Then tried to get it going. Battery fine, petrol in, oil ok. It wouldn't go when i tried to kick start it tho. I was trying for a good five minutes and nothing. Then I replaced the spark plug, and it started on the second kick! Here's the problem, the first spark plug was new, and not spoiled in any way. It went in shiny, and came out just as clean. When it was running, it was idling high, so I reduced the stop screw down till it was running relatively low, then I did it a wee bit too far and it cut out. Then it would not start from then on. Even after I put the stop screw back up to try and get it started, and nothing. It will no longer start now. It has fuel, it's battery and oil are fine, and it's just the same as it was before I started the whole thing, but nothing. I replaced the second spark plug in case it was spoiling them, but it came out clean as well. And the new one wont start it either. Does anyone know what I can do or check to see if I can get it going more reliably? When it runs, it sounds quite smooth, for a 2-stroke. But once it runs once, and stops, it wont run again anytime soon. And i'll be kick starting the hell out of it, and nothing, not even a splutter. I doesn't appear to be spoiling the plugs, so I don't think that's a problem. Thank you for any help or advice you can give me on this one, because its driving me crazy!! cheers, Atocp

Hi all, First off, a big thank you to JimR, mervin and all the others that have helped me thus far. I finally got my bike running yesterday after replacing the studs, bolts and washers as advised. As for the spark plug problem, you got to love Super Steel epoxy weld. That stuff is suuupper strong! Here comes the problem now. The bike doesn't idle. And there is an excess oily residue coming from the exhaust. I can put this down to either too much oil in the mix, or not enough fuel i guess (both really the same i suppose). Making the mixture harder to burn and therefore not run well. I have tried to adjust the oil pump, but haynes tells me that the carburetor, when at full throttle, should have the valve slide moving upwards till the little circular marker just hits the top. Here's the problem, when at full throttle, the valve slide goes waaayyy past that. In fact, it goes up pretty much till it hits the top. I have tried adjusting the throttle stop screw, and cable adjuster however neither seem to make a difference. Going from no throttle to full moves it far too far! What should i do to make the valve move less? Is it a cable problem, where the cable is too long? I wouldn't have thought so as the throttle grip can move quite a bit. Is there a well known way to fix this problem? Until I fix this, I cant guarantee that the oil pump is correctly set. And in any case, it shouldn't do this. Once again, this probably wont be my last time here, but thank you all for the help and advice, and any more is greatly appreciated. cheers, atocp

Hi Jim, Thanks for the response on the cylinder. The studs aren't that great to be honest, and the nuts are pretty rubbish as well. But I was sure it was screwed in tight enough. The replacement head had its stud holes slightly closer to the block. So when i put on the nuts, I had to add in an extra 2 nuts to every stud so the top ones hit the threads. Imagine the studs being too long by an inch, so the threads don't catch. The brass insert appears to be homemade, because it's off centre, and the threads aren't properly made. So not only did the air come out between brass and head, but also spark plug and brass insert. As per your advice, I'm going to try and get new studs, as I'd imagine they are relatively cheap. Although to use with the new head means some good old bodging. Thank you once again for the advice and help, cheers atocp

Hi there, Anybody got any ideas how i could seal the old cylinder head where the spark plug goes in? Or can i use instant gasket where the cylinder head and block join (including the metal gasket)? Thanks again for any ideas or advice atocp

Hi there, I finally got my yb100 running for the first time since i got it 2 years ago. It ran for about 4 seconds, and was the proudest moment of my week. Now the problems: I took the original head cylinder off and replaced it because someone had drilled out the spark plug threads and inserted a brass fixing to take the spark plug. No doubt a replacement for stripped threads. But it isn't tight, and air leaks out past the spark plug and brass fitting, even after a good helping of instant gasket. Is instant gasket usable in this way or is there a better method? The used replacement cylinder head wasn't an exact fit, and the metal gasket doesn't make a proper seal. So when it was started today, the exhaust came out between the cylinder and head. Should I add something onto the metal on each side to create a better seal? Or replace the seal? It was new just a few months ago and hasn't seen any running till today. The other problem is I broke the kick start leg. Snapped through the metal with a great big kick. On the upside, I have a replacement kicker and thats been fixed. 1 out of 3 aint bad for me!! If i need to replace the cylinder head, its gonna cost me about £66 at a yamaha dealer. And although im gonna go to a scrappies tomorrow, if i need to pay 66 quid, its gonna be night night for this motorcycle project for now! If anyone can help with any fixes to either of the first two problems, it would be an amazing help. Getting it started today was like a milestone, even though it was only for 4 seconds. And to get this far and have to give up seems such a disappointment. Thank you in advance for any help or suggestions, cheers, atocp

dont know the exact measurements, but if you search ebay for Yamaha YBR125 '05-07' Direct Replacement Fork Seals they come up, at a reasonable price. and going by the name of the auction, it would be 'against the law' to have something different. but then again, it is ebay. atocp

Hi JimR, The voltimeter had the options 2M, 200k, 20k, ->2k and 200. The 200 was the only one that seemed to get a reading when I connected the ground and the wire. And the same reading was given when i tried the HT and ground using either 200k or 20k. It just changed itself automatically to read the same value. I will go away and read up on the Haynes manual and see what I can do about the timing. I have a new ignition coil on the way. But i'll check the timing before I install the new one. Thank you again for the help JimR, very much appreciated. cheers, atocp

First and foremost, I'd like to point out I never did physics at school. An whereas I can tinker to get something working, the proper procedures usually aren't followed by me when it comes to electrics. Question: I have a YB100 and I believe the coil may be faulty. I set the Voltimeter to 200 (not 200k) and tested the ground and the 'live' to the negative and positive respectively. It gave me a reading of 2.4. I then put the voltimeter to 200k and tested the ground and the HT lead, and got a reading of 6.3. I then did the same but replaced the plug cap to the lead, and got a reading of 10.9. Does anyone know if this is anywhere near the correct readings? I checked haynes, and it talks about 0.17ohms +/- 10%. But I don't seem to get near those values. Even after changing the voltimeter settings. Does this sound like it is time for a new coil? I have a feeling it might be. I just bought a new NGK spark plug cap, would it really throw the readings as much as it has, even with a new coil? As always, thank you for any advice and assistance you can give me. cheers, atocp

just a simple quickie here, the sparks from my (not got it running yet) yb100 is few and far between, and weak at that when they do appear. gonna get a new ignition coil, but the ones online all have just 1 wire, whereas the original has 2. is it just a case of connect the positive, and ignore the (now redundant) ground black wire? cheers for any help, atocp

I dont actually know if the engine will run. I got the bike for free a couple of years ago, and having never ridden...rode...rided....having never driven a bike before, and having to reconstruct this one from scratch over the past year, im only at the point now, where I am in a position to run the engine. I will do as you suggest, and leave the loom as is for now. And I shall try and get the engine working first. The battery is brand new, and was giving out 6.8V once it was made and charged. But I will top it up with a little trickle charge. Thank you for the help Jim, no doubt I will be back on in the next few days if things dont go to plan! Cheers again, atocp

Thank you Jim for the quick reply. As its a relatively small bike, and a simple wiring harness, would it be advisable to remove the wiring, and get it working, OUTSIDE the frame, before the bike is started? The rear break light doesn't come on at all unfortunately. The tail-light element glows, but when the brake is pressed, the tail-light element goes out, and the brake light element doesn't come on.

Ok. This is quite an easy, or straight forward question. But this is my first bike, and I haven't had it running yet. Its the electrical thats tripping me up! I have wired up the bike, by using the Haynes Manual. Unfortunately, it doesn't seem to have a wiring diagram for the exact wiring loom i have, as things should be in block connectors when they aren't. The question is this....I have the electrics running, but the headlight and full beam wont work. The bulbs are fine, and the connectors are in the right place. Will getting the engine going if connectors are in the wrong place do damage to the electrics? Do the electrics work any differently (apart from running brighter etc) from when it is running from the engine, as opposed to battery alone? There are a couple of other wiring problems im having, like the tail light permenantly on until I hit the brake! But for now, i'd settle for solving this one! Its a YB100 1989. 2U0 Model. As always, any help is much appreciated. Thank you, atocp

Thank you Drewpy, You managed to write your reply while I was writing mine. If others have done it, I might try it. As long as im not making something that is gonna fall apart and coz a leak. Did you just use a bit of engine oil when applying the gaskets as normal? Thanks again. atocp

Thank you for the reply mervin If it didn't seem to cost about £20 for some make your own gaskets I would. But as I said, I already have a full set of gaskets. The pack I have is unopened. So I might be able to send them back, if I have the wrong ones. For a bike thats worth about £150, its hardly worth it spending tonnes of cash. Unless there is a cheaper way to make them? Are gaskets just card with a kind of rubber coating? A You Tube video that suggests a paper bag, or even phone book covers? Insane? Thanks again, atocp

Hi everybody, I am experiencing the joys of things going wrong while fixing up my 1989 yb100. I decided to replace the gaskets, as i need to take apart the engine anyway and the bike hasn't run in about 10 years. I bought a new full gasket set for the yamaha yb100 87-92, and went to fit the carburettor cover gasket , but the one i've bought doesn't even vaguely fit the same shape!! Does anyone know if within those 5 years the shape of the engine changed? Or were there different engines? I double checked on ebay and one picture, similar to the set i bought, shows the exact same gaskets. However, on another ebay item (a lone carburettor cover gasket ) does fit the same shape. I dont really want to buy one gasket that costs the same as the full gasket set i already have!! Any help would be most appreciated, thank you, atocp

thanks for the replies. measuring them would have been the most logical thing to do. next time im gonna spend a couple of days brainstorming to think up logical things before i post. thanks again atocp

Hi there, I was wondering if anyone knew what size fork seal went onto the 1987 Yamaha YB100? I bought a pair from Wemoto, and the said 26MM Forks 26x37x10.5. However they seem a little tight. A mechanic told me they would be tight to fit, but this seems a bit too tight. Motorcycle Products sell a pair for the yb100, but they are 27mm x 39mm x 10.5mm. Does anyone know if the 26 are right, and i should just be trying harder? Or is 27 in fact the correct size, and they should slide on relatively easily? Once again, thanks for any help and advice atocp

Cheers for the help. I have just successfully bought some of the parts from ebay that i was needing. as for the others, its gonna be out with the measuring tape and for some springs. i'll find out what parts i am going to be needing next. thanks again for the offer, very much appreciated. atocp

thanks for the help. i've found a used tap for the yb100 but dont know its condition. if i fail, then i'll buy some fs1e parts and give them a go. cheers, atocp

Hi there, I recently got a 1987 (i think) YB100 for free. And apart from some minor wear and some missing parts, it was pretty much all there. I am however missing some parts that are essential. Does anyone know if the following parts from a FS1E would be ok in the YB100? I can get parts for the FS1E a lot easier, and I am finding difficulties in getting the required ones for the yb100. The fuel tap. I can get a fs1e 12mm tap. The brake rod. Are they pretty generic just dependant on length and diameter? Springs for the centre stand, brake pedal and back brake switch? As you may realise, this is my first bike and im tackling everthing on it myself. All this before i've even taken my CBT. Thank you for any help or advice given, much apprectiated. atocp