NC30 Cylinder temperature imbalance

[owen_captain]

Hello guys. Yip its being awhile and I surpose thats because I've being running my bike sucessfully for the last two years without issue. Well, at least until now . I'm hoping some1 has had a similar experience and can guide me in the right direction . Here's my problem. On my last outing with the bike I noticed a "tappet" like noise coming from the front left cylinder region which seemed to worsen after warm up (it's closer to the head than the block). The bike also has a slight backfire which also started about two months ago and this started after I accidentally filled the tank with lead replacement fuel. My initial thought was its probably running rich so every chance I got I topped up with unleaded to dilute, but that was about 4-5 tanks ago and I still have the back fire. Anyways, Last night I started the bike up (on choke) and once warm, I checked the temperatures of the exhausts at the closest point to the cylinder head using my laser thermometer and whoa here's what I found. Front left was at 254 degC, and the other 3 were at about 150-160 degC. So I just switched off and thought of you guys . Any Ideas?? I doubt the lead replacement issue has anything to do with it, but I thought I'd just add that in seein as thats what started the initial back fire, but it may just be coincidental unless I burnt a valve or something.

Valve clearance?? but would that cause such a discrepancy?
Piston slap?? Oil hole or rings maybe?? rings were mic'ed before installation.
burnt valve/s perhaps?
Carb need balancing??overfueling in that cylinder??

I dunno, just throwing some thoughts out there.

Q, when using choke, does it richen all 4 cylinders or just 1 (perhaps the front left )? cause also, maybe I checked temp to soon after warm up. I'll retry tonight, but my worry is why such a huge discrepancy, so I'm appreciating all your help and experience and expertese .

Thanx
Cap

[Neosophist]

first off

lead replacement fuel shouldnt make any difference to the richness of the bike at all. it contains a small amount of additive to stop valveseat wear on older engines, just like super unleaded contains additives to clean the engine more.

the bike was deisnged to run unleaded 91 gas or higher but anything that meets the octane rating leaded or otherwise should be ok

almost every nc30 in south africa always ends up dying a brutal death >.<

how is it actually running? did you use the thermomomenter correctly?

Have you checked the valve clearanaces recently? any unexplained suddent tapping noise should be investigated striaght away without running the bike more.

you could have some carb / fuelling problem on that cylinder which might be why your getting a backfire, if its being starved of fuel it could be super lean which will burn your valves out if it hasnt already done so and ruin the engine.

start by getting the tank off and checking the vavles so you can rule them out, adjust and set them while you are in there.

check the carbs too, do all the slides move freely, is there any blocksages or shit in the fuel bowls? are they seriously off balance?

collant blockage / oil blockage?

the choke works on all 4 carbs.

hard to say without looking but theres a lit of things to start off with.

get the valves and carbs checked anyway then recheck your temps

[owen_captain]

Hey neo. Thanx for the reply. We can always count on you yeah in sa the guys ride bikes very hard. Lol. But I'm a guy that likes to take care of my stuff. Wen I did get the bike it was ruined and took me a lot of blood sweat n tears to get it going. So I pulled of the carbs and stripped them today. Checked floats, checked an cleaned emulsion tubes 4 hole in front 5 hole in back, pilot jets, main jets 115 front and 118 rear. Float height it thought I'd set it while there to 6,8. Alllookedpretty good. Checked butterflies. All balanced no play on the linkage and all opening at same time even at the slightest touch. Then I decided to open and check the needles. Firstly I checked that they moved freely and weren't jamming in any way even on the bike. Started for a few seconds with airbox off and all were working in sync. Opening and closing. Wen carb was off I opened up each one. While the, I thought iddo thecammo mod but I front left chamber (where I'm have the inconsistency), I found an incorrect spring it was hard and rigid and longer than the spring from the other three. I'll try attach a pic. This is the tiny spring between hr needle and the little retaining holder. Its about 10mm long. I'm hoping this is my problem. I will check valve clearance later today while everything is off but I'm hoping this is my prob. I managed to find a spring of same length and springyness and will try that in the meantym. What I did as well, is put an original spring in that chamber and my replacement in front right to rule that out it front ryt still heats up more. Will kept you in the he loop with further developments as I go along.

PS.. The tappet noise is not excessive and only comes in wen bike is hot.

[owen_captain]

I mean, to rule out that if front left still heats up kwiker than the others.

[newtothis]

Can you do a compression or cylinder leakage test? If swapping carb bits around hasn't changed anything it would be worth checking the exhaust valve is closing and sealing properly. If it's leaking on the power stroke the mixture coming out will be hotter than on the exhaust stroke.

[owen_captain]

Hey all, just to keep you guys in the loop, so while all was off. I did a valve clearance this weekend and most are within spec bar one or two, but very marginally out (mic'd the shims and will be getting those soon. Nothing to wow about though. So I packed it all up, carbs back on, funnelled them, offed the kill switch and pressed the red button. She fired on the turn without even opening the choke. Blipped the trigger a bit to get her up to temp, set idle at about 1200rpm and no back fire nothing. Had to top up fuel in my coke bottle funnel to keep it going and did my temp checks all hovering about 150 deg wit water at about 78 deg. Throttle response was also better than its Eva been incl dropping to idle nyc and kwikly. Even sounds sweeter than its ever been. Haven't taken it for a spin yet. Will do so once I put covers back on it just goes to show. Two years later and I still find some dodggy work from previous owner. The tappet sound didn't come back though, but will see after a run. It cud be because of the excessive heat in that chamber. Will let you guys know how that goes. I did the cammo needlesetup so dying to see how that pans out.

[Icemaestro]

So what did you do to fix it??