hey BFTP stoked to join, this is my story so far. i bought an unfinished cafe racer project a few months ago. re assembled the newly painted bike got it running (and it looks sexy as hell) so took it to henderson yamaha to have it tuned up for the new pod filters on it. thats when it all went wrong after waiting for weeks to have it looked at the technician said this model was very dependant on the airbox preassure so the pods wouldnt work, so i put the old air box back on and they took it for a test ride, gave it death, where upon it blew all its oil out the breather pipe. the bike has a flat spot from 5-7rpm and they recon that the engine is probably tired and needs re boring citing that air was getting past the pistons and pushing to much pressure into the crank case, forcing the oil out the breather. buger. does this sound about right? they also broke my new wing mirror and said nothing and i didnt see it until i rolled it out of the van at home. so, if i need to and or after i get it rebored id like to find an older mechanic or just one that knows a bit about these older bikes. any suggestions? i found the staff at henderson yamaha couldnt have been more friendly , but totaly useless in my case. ill post some pics as soon as i can! cheers
hi and welcome to bftp mate! ohhhh....sounds a bit nasty..pressurising the crankcase, would a used 750 or 900 motor with less mileage be a cheaper option and potentialy less of a headache? just a thought, good luck with the project
Hi T-Thunder13. Not many modern day mechanics know how to tune our old beasts. If they fitted pods to your carbs, they needed to increase the jetting and needle positions to compensate for more air getting into the engine throughout the rev range. Does your Yamaha have a metal air box with a breather pipe from the cam covers. If so, it may be blocked and be pressurising your crankcase. Is the engine leaking oil out of areas like the cam chain tensioner and tacho drive. If so, these are common leakage points when the crankcase can't breather. My GS 850 had a pressurisation problem which was caused through a blocked breather pipe. Not saying that yours has , but it may be worth checking. You could do a compression test too, just in case the rings and bores are worn out. How many kms has the engine done?
hi T-T. i'd adjust the valves and do a compression test first. that'd give you a good indication of the top end health. for the carbs/pods i'd buy the jetting kit, that's the best bet for anyone who doesn't have heaps of experience tuning carbs. i try to stay away from the bike shops as i found i can often find more relevant and accurate information online and if you're mechanically inclined at all it saves you lotsa money, too.
Hi TT13, they way we are going the XJ will be fixed by the weekend ;-) Good to have another Yamaha in the group.
Hey TT13, Ten months ago I would have reccomended the shop you took your bike to. Changed owners, changed mechanics and the guys trained in Oz to run the dyno are gone... The parts guy is back, and is pretty good at sourcing my odd requests, was in there today actually. psyguy - Today 20:18 hi T-T. i'd adjust the valves and do a compression test first. that'd give you a good indication of the top end health. for the carbs/pods i'd buy the jetting kit, that's the best bet for anyone who doesn't have heaps of experience tuning carbs. i try to stay away from the bike shops as i found i can often find more relevant and accurate information online and if you're mechanically inclined at all it saves you lotsa money, too. Yep, that would be the path I would follow too, plus get a workshop manual, even a scan off the internet will do. As Diesel has said, they don't see bikes like yours all the time anymore, even if you can supply a spec to the mechanic - as in glean what you can from the manual about how things should be and pass on that information if you have to put the bike in a workshop. I would try and sort it out yourself, but before you change anything, take notes, photos etc before you touch anything. So at least if you can't fix it, you can return it back to how it was. Mechanics hate getting failed home jobs eh Motu?
Cafe Racers Rule! Ahem, ok, glad to have got that off my chest.
Cheers guys thanks for the welcome! The engines only done around 47k so I would have thought it shouldn't be that buggerd for a 750, I have thought about a transplant, but I'd like to find out what the problem is first, I recon a compresion test is definately a good idea, Ive got the manual and have used it religiously through out the assembly, I just don't think the guy who started the make over on her would have gone to so much trouble if it had been running so rough, so maybe I'll just take the engine to bits to see if every thing is where it should be, because even with the correct amount of oil in it, the oil lamp Comes on after a few Minutes of running
Re; Oil pressure. If I am in doubt about oil pressure I screw in a car aftermarket oil pressure guage and get a reading. The oil light pressure swtiches are not always accurate and it may even have the wrong switch put in?
so fellas,yesterday i took the oil out of it and there was about 2 1/2 litres too much in there!! shit!! and after i did it went much better no oil through the breather and in neutral i can rev through the flat spot but it still goes weak when its in gear on the road at 5g,and when it hits around 5gs it backfires a bit too. recon ill take it for a hoon for a bit longer and see what happens, maybe itl smooth out? so a bit of progress there. with the recomended oil amount in it , the oil doesnt show up in the viewing glass at all. it seems to want about an extra 500mls to appear. should i be checking the oil level when the bike is running or when its off? it doesnt say in the manual. cheers
2 1/2 litres too much.. I would have thought it would be over the sight glass. Oil should be checked with motor off. I'd be inclined to put a new set of plugs in it as I've had issues with poor running due to old petrol and the plugs don't respond to cleaning....just looking at the cheap stuff first... Maybe clean out the carbs as crud can build up on the jets. check the fuel tap filter too.... keep us posted.
I was talking to a guy with a XJ900 that has done 140,000 kms. Long lasting engines aye
if you've replaced the oil filter then you need to run the engine for a while for the filter to soak up some oil and then check the oil level again. but wait for a few minutes till the oil settles before looking through the glass.
Good to hear that your problem was caused by to much oil. Yes, the engine needs to be off and sitting on the main stand, on level ground for a while before doing a visual at the case eye. Don't push your bike for too long past the 5k barrier if it's stuttering. This is a classic sign of severe leanness and you'll do some serious damage to your engine if you don't get your needle/main jet combo sorted. With pods, you usually need to change the needle shape and the main jet increase is sometimes as much as 3-4 sizes up.
Welcome to the BFTP and our back yard down home emergency repair advice sessions. Main things, bike on main stand, check site glass. Add oil if required till you can see it mid way between markers on case. All the guys have got valid and accurate points and you should check out each one asap, especially the one about thrashing an engine peaking at 5000 rpms and leaning out too much it will go BANG. Yamaha engines go forever, my old coal burner has done over 110,000 K's and is still going strong. Time I checked a few things over on her though, covers are beginning to leak a bit these days, so looks like I've a few things to check too. Take care and get that babay back on the track where she belongs.
