Alex. Posted October 11, 2014 Report Share Posted October 11, 2014 Hi Guys, I have acquired a bike that has been sat in a garage for a few years, which is in remarkably good condition. All is good apart from some rough running. The carbs have been cleaned and petrol changed, which has vastly improved matters, now it actually runs and rides! With a little choke on, it revs smoothly up the range and will hold constant revs at 2k without complaint. Knock the choke all the way off and it is reluctant to rev and holding at 2k it pops and bangs, bit of a backfire and generally not happy. Could this be a tweek to the carb settings, maybe mixture? Air leak in the mounting rubbers? I could run around with the choke on, but it's not right and I'd like to get her spot on. Alex. Link to comment Share on other sites More sharing options...
jaycee Posted October 11, 2014 Report Share Posted October 11, 2014 LOTS of carb cleaner. Strip the carbs off the bike, do NOT break the bank apart into th individual carbs*. I bought a set of carb files to clean the jets on my FireBlade, but was concerned about damage and git lucky wth just lots of carb cleaner and a run or two through the dishwasher followed by another blast of carb cleaner. Generally though, you may find you need to clean the crud out properly though. *took me almost a week of frustrating nights to get mine back as a group of four Link to comment Share on other sites More sharing options...
lorenzo Posted October 11, 2014 Report Share Posted October 11, 2014 How does it idle without the choke? The reason I'm asking is that 99% of the time a pilot jet will be blocked, it's about the most common thing for a bike that's been stood. Take the jet itself out, slop a load of cleaner down the hole and blow it out with compressed air. Do the same with the jet. Do the mains while you're there, but it's unlikely to be those really. When you rev it up, do the revs hang when you try to get down to idle again? If so, this means it's lean, so look for split rubbers & air leaks. Your line about mixture settings, apart from at idle, there's no such thing; they're pilot screws, they'll do tick over and maybe about 200rpm above that. Certainly they're not the difference between a bike running or not. Link to comment Share on other sites More sharing options...
Big_Kingy Posted October 11, 2014 Report Share Posted October 11, 2014 Could it be as simple as adjusting the rev idle screw? Link to comment Share on other sites More sharing options...
Wildbill Posted October 11, 2014 Report Share Posted October 11, 2014 It's short of fuel; reclean the jets and poke a bit fishing line through them and ensure the air filter fits correctly. Popping and banging is a weak mixture as proved by the choke helping smoother running. The air screw primarily effects the idle circuit but does have slight influence throughout the range of throttle openings. The idle screw; as you may sumise from it's name, only holds the slides open to prevent stalling at idle.Once the throttle is opened it has no effect on carburation. Link to comment Share on other sites More sharing options...
Alex. Posted October 11, 2014 Author Report Share Posted October 11, 2014 So another clean of the carbs, concentrating on the pilot circuit? I can do that! Just need some more time in the garage, better do some negotiation... ;-) Loz, I'm not sure how it will idle without choke, or if the revs hang, I just got the bike back together yesterday before I had to stop for tea! Alex. Link to comment Share on other sites More sharing options...
lorenzo Posted October 11, 2014 Report Share Posted October 11, 2014 Pull the pilot jets out, have a look down each of them, blast 'em out then have a look again. it's not uncommon for a bit to have gummed up in there so you'll be able to see light but it won't be fully clean, just a partial blockage. Obviously, with the holes being so narrow it's easier for these to get clogged. Link to comment Share on other sites More sharing options...
Evilchicken0 Posted October 12, 2014 Report Share Posted October 12, 2014 I guess you've balanced the carbs as well Link to comment Share on other sites More sharing options...
Alex. Posted October 13, 2014 Author Report Share Posted October 13, 2014 Pull the pilot jets out, have a look down each of them, blast 'em out then have a look again. it's not uncommon for a bit to have gummed up in there so you'll be able to see light but it won't be fully clean, just a partial blockage. Obviously, with the holes being so narrow it's easier for these to get clogged. Well, I gave them another good clean yesterday and even took the emulsion tubes out for a blast of cleaner. I left all jets in a bath of cleaner while I attended the bodies, then blasted with aerosol cleaner. No real change. The idle without choke can be a bit hit and miss, sometimes stalling, sometimes a bit low/lumpy. Still running rough. My next thought was maybe the spark plugs, they were changed a couple of hundred miles ago, over 10 years back! I guess you've balanced the carbs as well You'd guess wrong... I've never needed to balance a set, could an imbalance in the force cause this type of dodgy running? If so, you wouldn't happen to have some balancing kit, would you... Alex. Link to comment Share on other sites More sharing options...
lorenzo Posted October 13, 2014 Report Share Posted October 13, 2014 I know it sounds silly, but is it on the original battery? When I recommissioned a suzuki some time back it'd just about start on the battery that was in it but it really struggled to rev out cleanly. I think that the battery was struggling to cope with the whole spark plug thing as it'd hadn't recovered from just managing to turn it over, and hence the spark was too weak to get it running properly. I swapped the battery and it all came good. I'm not saying it's the battery, but the idea that it's blocked carbs, just because it has carbs, might just be a red herring. Link to comment Share on other sites More sharing options...
Alex. Posted October 13, 2014 Author Report Share Posted October 13, 2014 Good point Loz, I am thinking that the carbs are nice and clean now. There were a couple of times that the battery struggled to start the bike and when I put it on charge it didn't reach full charge before I had to go for the MOT. As the last time this bike had an MOT was in 2003, looks like I'll spring for a new battery too! Alex. Link to comment Share on other sites More sharing options...
Evilchicken0 Posted October 13, 2014 Report Share Posted October 13, 2014 I've got an air flow meter, which can be used for balancing Link to comment Share on other sites More sharing options...
exuprob Posted October 13, 2014 Report Share Posted October 13, 2014 2nd for the Carb balancing. I spent a longtime this year chasing a problem with my carb'd R1, popping and banging, running on 3 cyls at idle with the other cyl chiming in once the throttle was opened with general shite running at a constant throttle and balancing the carbs cleared it all up. Not to be discounted. Link to comment Share on other sites More sharing options...
kens Posted November 2, 2014 Report Share Posted November 2, 2014 Not forgetting the classic air leak downstream of the carbs, leaning it out. Inlet rubbers perished, split or cracked and letting air into one of the inlet tracts. You'll get 3 plugs looking rich and the 4th looking different. Diagnostic could include spraying carb cleaner in and around the rubbers while it runs - if the revs increase, you've found the leak. Or set your shed on fire, which could also happen. Link to comment Share on other sites More sharing options...
Alex. Posted November 17, 2014 Author Report Share Posted November 17, 2014 Right, more progress made and some bad news... First off, the choke at idle issue, this was down to the idle speed being set far too low! Upping that adjuster allowed the bike to idle properly, once warm. Still a bugger to get started from cold. I made up a set of the carb balancers, as shown in PS and tried to use them. The carbs were not showing equal balance, but then they started moving. The oil in the tubes would stay still for a short while, then move in either direction with no other outside influence. A chat with BudgeBoy assured me that I was using them correctly, but with a low idle, so I upped the idle. It made no difference. Further investigation required. As I thought that there was an underlying problem, other than the balance or pilot circuit, I looked elsewhere. Spraying carb cleaner all around the inlet rubbers did not provoke a change in idle, so those are not leaking. Next up was a compression test. Nuts. Low compression on the right cylinder, with some of the other not much better. Haynes book of lies states compression as standard 148psi, low limit 120psi. Measured pressures, left to right:- 140 - 120 - 110 - 105 Looks like a bit more surgery required and probably the reason an obviously well looked after bike was laid up over 10 years ago! Next up is to redo the test with a bit of oil down the bores to see if it is top end or rings. If top end, I'll check the valve clearances before pulling the head off to have a look. There goes the quck fix! Alex. Link to comment Share on other sites More sharing options...
thefatman Posted November 17, 2014 Report Share Posted November 17, 2014 If you measured it from left to right then check the compression with a fresh battery going right to left as a weak battery can give lower readings by the time it has had to turn the other cylinders over. Link to comment Share on other sites More sharing options...
Alex. Posted November 17, 2014 Author Report Share Posted November 17, 2014 If you measured it from left to right then check the compression with a fresh battery going right to left as a weak battery can give lower readings by the time it has had to turn the other cylinders over. I thought of this at the time, so went back and rechecked the first cylinder. It was still reading 140psi. Alex. Link to comment Share on other sites More sharing options...
BudgetBoy Posted November 17, 2014 Report Share Posted November 17, 2014 Do the oil in bore test and then see what it is.. Id suspect it is your rings as its been sat, in my experience they sometimes get stuck in the piston grooves due to the condensation build up (surface rust in bores) and pressure keeping them in. I'd do a leakdown test to pinpoint it. Could also be a warped head or naffed HG.Or as you say valves. Lets hope its the valves sticking or out of adjustment. Link to comment Share on other sites More sharing options...
Alex. Posted November 17, 2014 Author Report Share Posted November 17, 2014 I'll probably be doing the oil in bore test on Friday, unless the missus car spectacularly fails it's MOT... Lets hope its the valves sticking or out of adjustment. Very much this! Alex. Link to comment Share on other sites More sharing options...
Wildbill Posted November 17, 2014 Report Share Posted November 17, 2014 Have I missed somewhere that states what bike it is ? I would also be running it through a few heat cycles if stuck rings are suspected before pulling a head off on an ILF due to the price of gaskets. Link to comment Share on other sites More sharing options...
Alex. Posted November 18, 2014 Author Report Share Posted November 18, 2014 I'd not said what bike, as it's not very PB! It is an '88 Yamaha FJ1200, with top box. I have run it through some heat cycles, even ridden it on the road a couple of times. It is fully road legal with MOT and everything, but just does not run as smoothly or as powerfully as it should. Alex. Link to comment Share on other sites More sharing options...
Alex. Posted November 21, 2014 Author Report Share Posted November 21, 2014 Turns out it is the rings! Dropped some oil down and the compression went up to 150psi. So, I've left some redex soaking in the bores to try and de-gum it all. Then a good thrashing, what could possibly go wrong... Alex. Link to comment Share on other sites More sharing options...
BudgetBoy Posted November 21, 2014 Report Share Posted November 21, 2014 Turns out it is the rings! Dropped some oil down and the compression went up to 150psi. So, I've left some redex soaking in the bores to try and de-gum it all. Then a good thrashing, what could possibly go wrong... Alex. I doubt it will do anything (IMO), its strip down time :-) Link to comment Share on other sites More sharing options...
Alex. Posted November 21, 2014 Author Report Share Posted November 21, 2014 I doubt it will do anything (IMO), its strip down time :-) That shouldn't be a smiley face, lots of money and time, in relation to the cost of the bike! Redex was suggested by the FJ forum lot, it's worth a shot. Alex. Link to comment Share on other sites More sharing options...
BudgetBoy Posted November 21, 2014 Report Share Posted November 21, 2014 That shouldn't be a smiley face, lots of money and time, in relation to the cost of the bike! Redex was suggested by the FJ forum lot, it's worth a shot. Alex. Depends on how you see the smiley face.. I see it as great,, get my hands dirty and dissect and engine.Save the bike/engine from the scrap heap whilst at it. Sure you could get another engine but less fun and history unknown. As i said to you im a Pm ages ago.. If you are going to keep it then its worth going through the bike. if not, swap engine (for speed) and sell it on.. then part out the old engine.You should then recoup (over time) a bit of the money you pay for the other engine. Good luck and keep us informed Link to comment Share on other sites More sharing options...
Alex. Posted November 21, 2014 Author Report Share Posted November 21, 2014 Either the redex works, or I will be rebuilding the engine. BUT £240 on gaskets and rings, I'm hoping they free up! Alex. Link to comment Share on other sites More sharing options...
Evilchicken0 Posted November 22, 2014 Report Share Posted November 22, 2014 Take the top box off, its bound to be that Link to comment Share on other sites More sharing options...
Alex. Posted December 29, 2014 Author Report Share Posted December 29, 2014 Well, the redex did not work, so I have started stripping the engine! The head and block are sitting on my bench and they look acceptable with no obvious damage. Now I just need to decide if I'm going to split the cases or just do the top end. Some crud did drop into the bottom end from the base of the cylinder studs, as there is some rubber around the middle of the stud and this has long gone. I could just try a flush of the bottom end and hope all the stuff gets out.... I was going to replace the studs, but it looks like they are no longer available! Alex. Link to comment Share on other sites More sharing options...
Evilchicken0 Posted January 2, 2015 Report Share Posted January 2, 2015 Good to see you t'other day Could you get the studs powder or ceramic coated ? I'm sure you could paint them yourself with engine enamel but they'd probably corrode through again. Link to comment Share on other sites More sharing options...
Alex. Posted January 2, 2015 Author Report Share Posted January 2, 2015 Good to see you t'other day Could you get the studs powder or ceramic coated ? I'm sure you could paint them yourself with engine enamel but they'd probably corrode through again. You too, ta for the tea and cake. I still beat the missus home, she went shopping... I don't know quite what the rubber coating on the studs is for, but I'll probably just use them as is. The studs will probably last as long as the rest of the bike! Alex. Link to comment Share on other sites More sharing options...
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