christofeser Posted July 3, 2010 Share Posted July 3, 2010 Cut a long story short - had a breakdown yesterday about 100 miles from home on the A12 towards colchester... if anyone is from round there and kindly stopped to help me, thankyou so much Yet, I still had to get the AA to recover me (they took a long long time at a big big cost), because the bike wont start I discovered that it may be a fuel problem. The nature of my breakdown was similar to running out of fuel - i.e. full throttling it, yet, declining speed constantly... I was looking at the fuel tap this morning and took the second stage off to see if fuel was actually coming out. It didn't come out when on the "on" or "reserve" settings, yet comes out on the "prime" setting (I assume "pri" stands for prime?)... has anybody had this problem before and, if so, how do you fix it? Any suggestions? Regards Chris Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 3, 2010 Moderator Share Posted July 3, 2010 Chris thats a vaccum tap and when in on and reserve the engine needs to be running, the vacuum developed in the inlet manifold then opens the fuel supply. the PRI position bypasses this and gives a fuel supply constantly, you would for example use this position briefly if you had run the bike completely out of fuel. try the PRI position but it may be something else, not familiar with the bike in question but 'oldtimer' is a good person to ask. Having said this look for damage and melting etc at the reg / rec unit. Link to comment Share on other sites More sharing options...
oldtimer Posted July 3, 2010 Share Posted July 3, 2010 Cut a long story short - had a breakdown yesterday about 100 miles from home on the A12 towards colchester... if anyone is from round there and kindly stopped to help me, thankyou so much Yet, I still had to get the AA to recover me (they took a long long time at a big big cost), because the bike wont start I discovered that it may be a fuel problem. The nature of my breakdown was similar to running out of fuel - i.e. full throttling it, yet, declining speed constantly... I was looking at the fuel tap this morning and took the second stage off to see if fuel was actually coming out. It didn't come out when on the "on" or "reserve" settings, yet comes out on the "prime" setting (I assume "pri" stands for prime?)... has anybody had this problem before and, if so, how do you fix it? Any suggestions? Regards Chris chris,you say you were a 100mile from home when it started,when did you fill up and how full because it sounds like a fuel problem,if you had filled up before you set off and done a 100miles then it is possible that you ran out of fuel and did not switch over to reserve in time before the carb was dry and unless you switch to prime it wont fill the carb up enough for it to fire,sometimes when the carb is run dry a air lock can cause difficulty in getting the bike to run,other possible causes clogged fuel hose fuel tank breather hole or faulty fuel pump,what did the AA man try if anything some of them are useless when it comes to bikes! basically a bike only needs 3 things to run fuel, a spark and the right air mixture. at the moment the best thing is to check your getting a spark, and switch to prime if your getting a spark and the fuel is getting through and your battery is fully charged if it still doesnt start let us know and we will try to help. Link to comment Share on other sites More sharing options...
christofeser Posted July 3, 2010 Author Share Posted July 3, 2010 Spent all day with a savvy-biker diagnosing it. We've come to the definitive conclusion that I'm not getting enough compression due to f**cked up piston rings... Also, that the oil is being funny. The oil levels have been rapidly declining due to being burnt (someone said they noticed smoke the other day) - which I forgot to check. This may be rather costly to repair, seeing as it's an engine problem... Link to comment Share on other sites More sharing options...
Paulwhite Posted July 4, 2010 Share Posted July 4, 2010 well if its ur piston rings about to go then u wont b able to start it on the starter motor but you should be able to bump it. easy way to check (piston rings) bump start the bike keep it running for 10 min then turn the ignition off, turn ignition back on and it should start on the starter motor, turn it off again and let stand for 30 min then try the starter again if it dont start up then ur piston rings need replacing. but check ur oil 1st and hope and prey you havent done the same thing i did. see if the oil is ok (if its normal, thin, or like a white cream then post what you find) my bike did something similar when it decided to kill itself, was driving at full speed then it stuttered, then slowed down to a stop and wouldnt start up till it had cooled down, my 1st thought was fuel but id just come back from filling the tank, got it to my m8s house to strip down and found that the bottom end had gone! was gonna cost me £400 to get it fixed then id need to buy gaskets ect, or £500 just for the part (from the dealer!) so then the xvs 125 bobber was born......... but yeah get back to me on what you find but hopefully you have just run out of fuel Link to comment Share on other sites More sharing options...
Paulwhite Posted July 4, 2010 Share Posted July 4, 2010 Spent all day with a savvy-biker diagnosing it. We've come to the definitive conclusion that I'm not getting enough compression due to f**cked up piston rings... Also, that the oil is being funny. The oil levels have been rapidly declining due to being burnt (someone said they noticed smoke the other day) - which I forgot to check. This may be rather costly to repair, seeing as it's an engine problem... yes it would b costly to get the piston rings done unless you want to try it urself? if you wanted i could give you a step by step with pics(i need to do it to my bike next week ) but its quite simple if you have the right tools i.e socket set, allen keys, screwdriver and needle nose pliers. it just takes a while to strip the bike down say 2 to 3 days max for the whole job and thats taking your time and having a fag and brew every 5 min lol Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 Right... I really need it back on the road a.s.a.p so was tempted to just pay for a fix from a local mech (who usually quotes me half of what the garages do!) We think it's the rings because we put oil into the cylinder (to seal it around the rings) and that's what eventually got it just enough compression to get it started (instead of just trying to turn over)... I could also do a few things to it at the same time make it a bit sexier! I was thinking of doing a similar tank & fender paint job - matt black sorta look maybe? ANYWAY back to fixing the bike... I suppose I could try and do it - where would I get the piston rings from??? Cheers, Chris Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 Okay (sorry for double-posting) so I think I want to go ahead and try it myself. I emailed a yamaha dealership this morning to see if they could source some of the piston rings - anyone have an idea how much these would cost? Paul when are you starting yours? I'm looking to start VERY soon... It involves taking the engine out right?? That's explained in the service manual I think, and I MIGHT be able to manage it... I just want it fixed by next week (i dont mean monday! I mean the END OF NEXT WEEK LOL) Chris Link to comment Share on other sites More sharing options...
Paulwhite Posted July 4, 2010 Share Posted July 4, 2010 right you wont need to take the engine out but you will need to strip the bike! that means taking the tank off, seat off, carb off, air filter assembly/box, and exhausts, basically anything that is in the way of the cylinders! make sure you take note or pictures of what goes where when you take it apart especially the fuel pipes! then you will come across the plastic parts on the top of the heads, take them off (should be some small allen key bolts) then when you get all that sorted give me a bell and il go through step by step, as to the piston rings the Yamaha dealer should b able to get them in for under £20, but its allot easier to get new pistons with the rings on them (makes a 20 min job into a 2 min job) so look into how much new pistons with rings would cost (shouldnt be too much). but yeah im not sure when il b doing it next week (still got to sweet talk the misses lol) but iv had to do it 3 times already! so il have to get back to you on that one but yeah its easy peasy (if not a little messy and tedious) Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 4, 2010 Moderator Share Posted July 4, 2010 Dont forget you will need cylinder head gaskets x 2 and base gaskets x 2, bear in mind they may or may not be different for each cylinder. Also get your head around the valve / camshaft arrangement. be sure you know how to do the alignment of the crank and camshaft, I dont know about this bike but its possibly a chain driven overhead cam, find out. Also find out about the cam chain tensioner, you may need to slacken it to remove and replace the chain if it has one. Torque wrench settings and a torque wrench?? have you got these? Tip When lifting the cylinders, stuff rags around the crancase opening when it is exposed before the cylinder is removed, then if there are any broken rings etc they wont fall into the engine. we live in a digital age so take pictures and lots of them, these will show routing of wires pipes, anything really...just for reference later when its time to re-assemble it. Bag things and label the bags, front cylinder...back cylinder...front head...(you get the picture) Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 Wow this just got a whole lot more complicated Okay pretty much I stripped the bike down the other day to check the carb (which was, in turn, fine) so thats okay. Do I need to take carbs off - I didn't get this far (as didn't need to)? From what you've just said makes it seem a bit complex I have a friend who knows a bit about engines (not this one in particular) but could be able to help... although he works during the week. If I'm right from looking at the manual, it is a chain driven overhead... although I still don't have a scoobie what it all does/how it all works, and even if you tried to explain it I'm not the type to understand until looking at it myself... Why do I need head and base gaskets? Aren't they there already? Ach I'm so dumb Chris Link to comment Share on other sites More sharing options...
Paulwhite Posted July 4, 2010 Share Posted July 4, 2010 Dont forget you will need cylinder head gaskets x 2 and base gaskets x 2, bear in mind they may or may not be different for each cylinder. Also get your head around the valve / camshaft arrangement. be sure you know how to do the alignment of the crank and camshaft, I dont know about this bike but its possibly a chain driven overhead cam, find out. Also find out about the cam chain tensioner, you may need to slacken it to remove and replace the chain if it has one. Torque wrench settings and a torque wrench?? have you got these? on mine the cylinder gasket is metal (coated in plastic) and the cylinder head is a metal gasket and after 8 years they are still fine so iv used a little gasket sealant just to make sure and they are the same for both cylinders but if there worn, wemoto or e-bay is the best place to get new ones, it is chain driven overhead cam, the cam sprocket has a mark on it (for tdc) so iv marked the chain to that, so when i come to put the head on, it will go back on exactly as it came off, he will need to take the tensioner off, but the chain should be ok and it is a good idea to get the torque wrench and service manual! but the hardest part is stripping it and putting it back together lol Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 4, 2010 Moderator Share Posted July 4, 2010 Aaaaggghh i replied to this and it was lost in the ether!! On the subject of cam chains you need to be careful not to drop it into the engine. tie some string to each end and get someone to hold the strings while the cylinder is lifted (dont forget the rags). When the chain ends exit the bottom of the cylinder you can retrieve them and tie the strings to something to keep it all in place. Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 fakk I keep losing my stuff to!! Okay so I really dont know what we're all on about I'm quite lost. I don't really understand the layout and wont until I do it... Why would I need new heads and gaskets??? What will be wrong with the already-fitted ones? Are they costly too?! I'll probably want to start as soon as I've got all said parts, which MAY be one or two days - depending if the Yammy dealer has it :S Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 4, 2010 Moderator Share Posted July 4, 2010 I assume you will have to remove the engine from the frame. Gaskets both head and base will need to be replaced, re-use them at your own risk...I wouldnt but get a price and decide, Paul has re-used his with gasket sealant so you will need to buy this is you decide to do the same. Tip, when using any sealant on gaskets be careful not to get any excess into any holes or oil passages that may be present in the gasket. How would I know how much they cost? Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 haha okay I still dont understand what heads and gaskets are but im sure my friend will fill me in... If they dont need replacing - I'm sure he has some sealant too. And if he doesnt - it will still be cheaper than paying someone to do it right?? SO I will have a look around. Cheers guys Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 4, 2010 Moderator Share Posted July 4, 2010 This is not a small job for a beginner, personally I think you should get your (experienced ?) mate to do it and you play the willing assistant role or this bike could be tommorows 'basket case' Also you seem to be convinced that the rings are fcked! how do you know this for sure? You started off by saying I discovered that it may be a fuel problem. The nature of my breakdown was similar to running out of fuel - i.e. full throttling it, yet, declining speed constantly... Chris Now fcked rings would not usually cause a running bike to stop mid-flight so Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 Right, well. He is very experienced (he's had many many many a bike, and now owns a rover v8 trike which he built. He's not just some guy from college or anything - he's actually a mate's dad from a biker-family so...). He diagnosed it. From pressure readings, we got 120 psi from the rear cylinder (optimum is 170) and only 55 psi from the front. This was before the bike would even start. Pressure, at this point, was obviously the problem, as it started after putting a tad of oil down the front cylinder and it started (indicating that the oil sealed the cylinder to give it enough compression to start - or so we believe). Or are we barking up a wrongtree?? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 4, 2010 Moderator Share Posted July 4, 2010 Right, well. He is very experienced (he's had many many many a bike, and now owns a rover v8 trike which he built. He's not just some guy from college or anything - he's actually a mate's dad from a biker-family so...). He diagnosed it. From pressure readings, we got 120 psi from the rear cylinder (optimum is 170) and only 55 psi from the front. This was before the bike would even start. Pressure, at this point, was obviously the problem, as it started after putting a tad of oil down the front cylinder and it started (indicating that the oil sealed the cylinder to give it enough compression to start - or so we believe). Or are we barking up a wrongtree?? fair enough it looks like you mate has the job, good luck with it,watch and learn. only one other thing may have a similar effect and thats a sticking carboned up valve, this could cause the smoking and the compression loss just as much as the rings could. Link to comment Share on other sites More sharing options...
christofeser Posted July 4, 2010 Author Share Posted July 4, 2010 So can this be cleaned whilst the engine it out? Chris Link to comment Share on other sites More sharing options...
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