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View Full Version : Sporty Running on one! Dumbest Ever HELP!



CoLoNpEe
06-24-2014, 9:16 PM
Well! To top it off, putting new pipes on the Sporty, of course first 3 nuts come off the studs nicely, the fourth... SNAP! flush with the head and of course the one closest the frame! Buncha tools purchased and some shop time a week later and I have a the frigger out... Awesome! I install the new exhaust, fire up the bike and WHOA! Only one cylinder! Of course the dead one is the one where the stud broke. Rev it up seems to run on both cylinders, go to let it idle and pop pop pop... then a blue flame out the pipe, followed by the popping again. What the hell happened for this? Bike ran perfectly before I went to change the pipes...
Did the diagnosis... Electrical is fine... Compression test... 80 psi difference between the cylinders!!! I have a leak somewheres... could some carbon have gotten between the valve and seat causing the valve to not seat? When I do the thumb test... my thumb gets blown from the hole (with a lot of oomph, same as the other cylinder which is fine, so any piston/ring sealing problem is eliminated), but it doesn't get sucked towards the hole... this to me says exhaust valve isnt seating correctly...and cant build compression on the compression stroke... If I got a compressor, could I blow out the exhaust port and hopefully clear the crud away? I looked inside, the valve and exhaust chamber are clean (light carbon, no deposits at all, this is low mileage bike), What in the hell would have caused this other than the obvious something got in the hole.... what can I try before having to rip the head off? Any old school tricks? Could a gasket have gotten messed by heating the stud with propane? Im at a loss, any ideas before I tear this apart would be great! :banghead: To add, there was a new crush gasket installed, and this is seated fine as well, eliminating that also from the equation...

lxlmariuslxl
06-24-2014, 10:20 PM
It kinda sounds like you may have over heated the head and it cracked. I know with older cars you can put a dollar bill at the tail pipe and if it gets sucked in you you have a burnt valve. Assuming the cam doesnt have a crazy overlap. Good luck!

farmall
06-25-2014, 3:58 AM
I'd put air to it with a leakdown tester.

If no have dat, knock the guts out of a spark plug with a punch (wear eye protection!), grind off the side electrode, and weld a steel compressed air nipple to it.
I've made several of those as compression/leakdown tester adapters for different engines (the compression guage side gets a matching air chuck), and if you use a pipe nipple between the air nipple and plug shell they work great on buried plugs.

That will tell you where it's leaking before you pull the head.

CoLoNpEe
06-25-2014, 5:56 AM
I'd put air to it with a leakdown tester.

If no have dat, knock the guts out of a spark plug with a punch (wear eye protection!), grind off the side electrode, and weld a steel compressed air nipple to it.
I've made several of those as compression/leakdown tester adapters for different engines (the compression guage side gets a matching air chuck), and if you use a pipe nipple between the air nipple and plug shell they work great on buried plugs.

That will tell you where it's leaking before you pull the head.

The shop I go to was kind enough to lend me their leakdown tester! I have a compressor, now I have to buy a hose I guess!

CoLoNpEe
06-25-2014, 9:15 PM
Here's the news! Did a leakdown test and here is the following... exhaust valve as I suspected is not seating correctly! So, obviously the only thing that would have caused this is some carbon getting between the valve and seat causing the leak. Here is the next plan of attack to deal with that... going to buy some valve lapping compound... rotate the engine till the valve is open, put some compound on a Q-tip, apply it to the seat/valve from the exhaust port, rotate the engine again till the valve closes. Then I am going to take a leather lace or rope, fish it in around the valve and rotate the valve in the seat that way, then follow up with another leakdown and repeat if necessary. This should do the trick wish me luck!

Sky
06-25-2014, 10:20 PM
Sure the valve was/is closed all da way? Check your pushrods? might have adjustables, or a stuck lifter too. Bent/galled valves will hang open too.
Good luck with your cheats. I got lucky once replacing a valve spring without pulling the head, but really it's usually worth just pulling the head.
How are you going to clean out the lapping compound? Think about your rings/cylinders/pistons etc

surfbum
06-25-2014, 10:25 PM
pull that head and do it right. Pretty easy.

CoLoNpEe
06-26-2014, 5:58 AM
Sure the valve was/is closed all da way? Check your pushrods? might have adjustables, or a stuck lifter too. Bent/galled valves will hang open too.
Good luck with your cheats. I got lucky once replacing a valve spring without pulling the head, but really it's usually worth just pulling the head.
How are you going to clean out the lapping compound? Think about your rings/cylinders/pistons etc

Motor is stock low mileage 1200... no adjustables or cams or anything out of the ordinary... As for the lapping compound, I figure if the valve seats, well thats just going to burn off and blow out the pipe anyway... I wont have to use much as I look in the exhaust port and its extremely clean in there, just enough carbon must be there to eff it up

xllance
06-26-2014, 8:09 AM
How do you expect to rotate the valve with a rope? I'd say save yourself a lot of trouble and pull the head.

CoLoNpEe
06-26-2014, 8:48 AM
How do you expect to rotate the valve with a rope? I'd say save yourself a lot of trouble and pull the head.
I am going to close the valve so it just seats then do the rope trick... its worth a try... I have a whole weekend to try these things out before going the way of taking the head off. If it works put it in the old school poor mans book of tricks!

Davestune
06-26-2014, 2:17 PM
your wasting your fucking time

xllance
06-27-2014, 2:19 PM
If lapping the valves like that fixes your problem you'd better go buy a lottery ticket because you have incredible luck. I've lapped valves before and even on a bench with no spring pressure it takes awhile. I would imagine you couldn't even turn the valve by hand with the springs on. Not to mention the lapping compound scoring your cylinders like someone else mentioned. But nevertheless give us an update.....

CoLoNpEe
06-27-2014, 11:28 PM
If lapping the valves like that fixes your problem you'd better go buy a lottery ticket because you have incredible luck. I've lapped valves before and even on a bench with no spring pressure it takes awhile. I would imagine you couldn't even turn the valve by hand with the springs on. Not to mention the lapping compound scoring your cylinders like someone else mentioned. But nevertheless give us an update.....

Here's the update, finishing taking the head off tomorrow, looked like some carbon was forming tiny ring around the stem keeping it from going up all the way. I cleaned that the best I could, did my Qtip an lapping compound trick, started the bike after the pipe went back on, made an improvement, but still no luck. I have to lap the valve with the head off, and I am going to helicoil where the exhaust stud broke at the same time... who thought changing pipes could be so much fun!

Clockwork444
06-28-2014, 10:49 AM
my sporty would only run on 1 cylinder at idle, and would pick up the second one after revving a bit. the slide diaphragm was cracked and it wasnt lifting. one cylinder must seal better which isnt uncommon so it gets all the fuel till the rpm are up enough to draw the slide upward then the second cylinder would finally get some fuel and start making power. not what you'd expect out of a single carb bike but it happened to me. something to look at

farmall
06-28-2014, 5:52 PM
Internal lapping is extremely risky. Best check for even the tiniest bit of stray abrasive by pulling the jug to ensure none made it to the rings.

Lapping compounds are essentially "sand and grease".

I advise no one to try to lap an HD valve or any conventional engine valve in-place as described.
It's WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAY past negilgent even if you somehow get away with it.

Also, "holy shit!".

StrawbellyJam
06-28-2014, 6:25 PM
This thread made me wince, at least you're taking the head off now.

xllance
06-28-2014, 8:22 PM
Yeah I was sad to hear he violated the engine with lapping compound.....THEN pulled the head. Now the op has another issue yo worry about. Doh !!!!!

CoLoNpEe
06-28-2014, 11:29 PM
LOL, well the head is off and the verdict is.... gunk under the intake valve... little chunks of carbon kept the valve from closing. Now to get some new gaskets and get this P.O.S. back together....

Sky
06-29-2014, 6:01 AM
Better find out why that valve was hanging to allow the build up of carbon.
A good time to inspect is now
Bent or galled valve
Worn/damaged guide
Weak valve spring
Bad rocker/shaft
Over adjusted pushrod
Stray bits from the last quick fix, ha!
Good luck

xllance
06-29-2014, 12:39 PM
Man its gonna be worth your while to at least have new guides put in and do a valve job !

CoLoNpEe
06-29-2014, 3:14 PM
UPDATE: Took the valves out, all kinds of shit between them and the guides, how? well guides, valves seals are/were fine, fucking some shit from drilling and heating the stud area must have gotten in there. Cleaned everything up, lapped the valves, good as new! Tested the seat to valve seal, no leakage! Now for some new gaskets and back at it!