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Author Topic: Backfire, timing after rebuild need help!  (Read 778 times)

Me Too

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Backfire, timing after rebuild need help!
« on: March 28, 2018, 04:16:56 AM »

Hello again everyone!

Last summer was wasted. Every sunny day, every meet-up every cross town tour and every night ride was 100% shut down and destroyed due to a compounding series of issues I experienced with my bike trying to fix , waiting for parts and having ti go wrong.... now that the summer is ending I NEEEEEEEED to get this #@#$@-ing thing back on the road or I'm going to lose my mind.

Problem:

I eneded up re-building the rear cylinder. Did all kinds of damage in the process ( because of what started as a simple problem that I blew up into a major... super frigging major one.. ( NOOB) ) which included replacing; all valves, valve seals, piston rings, piston head. I've put it all back together to find I'm getting a backfire. Bummed I've waited until it was arm enough to start working again and just finished taking it apart to have a  look/ adjust the timing chain and BANG, again, no start/idol ( been sitting and need new starter :(  ) . I have pics to show where the Cam shaft/Chain is currently and the service manual that shows it should be 16 pins apart... where did i go wrong... im so lost guys.

I moved the magnito to the "R" position and lined up the indicators as it said in the manual...what is happening!?!? I couldnt get the cam shaft's indicators "level " with the cylinder head because of pressure from the valves so I slanted both cam shafts a little left to provide slack but lined up the chain as it should be...

Like if you could draw- along the face both cam shafts- a pointed arrow towards the ceiling and that pointed arrow  would make both cam's "upwards" or "90 degrees" then I rotated both shafts left so they would both be about 85 Degrees but I account for the rotation and was able to get the chain in the right spots 16 lengths apart....

Anyway, any help would be greatly appreciated.

Thank you in advance.... SO much!
« Last Edit: March 28, 2018, 04:18:28 AM by Me Too »
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Cloud

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Re: Backfire, timing after rebuild need help!
« Reply #1 on: March 28, 2018, 10:28:57 AM »


Is this for the GV650?

Front cylinder is F on the magneto rotor. Start by doing the front. IIRC she runs a wasted spark so any TDC is fine TDC. Once your F is lined up, then rotate the engine over less-than-one-rotation to get to the R on the magneto rotor, then do the cam uplining.

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Me Too

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Re: Backfire, timing after rebuild need help!
« Reply #2 on: April 02, 2018, 05:48:57 AM »

Maaaaaaaaaaan, you have to be my favorite person throughout he entire planet I have never met. You've given me direction, thank you, but I've given it another shot and would love to ask you if I should be able to line up the cams with the plane of the cylinder without issue or is it common to fight with the valve springs?

Yes it is the gv650, and the exhaust cam is unable to line up with the plane of the cylinder head without intense pressure from valve springs. Intake, no problem but the one just doesn't want to be upright.... thoughts?
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Cloud

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Re: Backfire, timing after rebuild need help!
« Reply #3 on: April 02, 2018, 03:47:56 PM »

If you're on-cam at |F or at |R on the rotor, per cylinder you've done it wrong.

The rear will be on-cam at |F and the front will probably be on-cam at |R

In theory, if we start with front cylinder, the |F TDC you're timing to should be -exhaust just closed- and -intake about to open- on the front cylinder. Then line up the timing marks, 16 links on the chains, and so on. Once that's done, you can more or less forget the front and everything it is doing.

Rotate the crank 285 degrees (or whatever) to get it to |R TDC. It'll be the same again -exhaust just closed- and -intake about to open- and the timing marks should be there the same, 16 links on chain, etc
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Hylife

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Re: Backfire, timing after rebuild need help!
« Reply #4 on: April 06, 2018, 02:26:09 PM »

Cloud is right.
Must first line up front cam marks when magneto is on the F mark.
Then using a socket, rotate anticlockwise "almost a full turn until the R mark on the magneto hits its mark and then get the rear cam marks and chain set.
Need to remove or back off the rear cam chain tensioner whilst you set the cam marks and then fit/release the tensioner afterwards.
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Me Too

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Re: Backfire, timing after rebuild need help!
« Reply #5 on: April 28, 2018, 03:51:10 AM »

Super late reply but thank you guys so much. I finally got it sorted.. after two MORE attempts to ling this !@!@ up I realized... and this goes perfectly with the ALMOST EVERY IMAGINABLE THING THAT COULD GO WRONG HAS GONE WRONG scenario I have been struggling through...... somehow... and believe me I have no idea... the cam shaft had slipped and was no longer aligned with itself. which explained why it wasn't able to line up flush with the cylinder head...

Unbelievable. So many of these "thaaaaats impossible" moments has happened to this thing over the last summer and into this one, that I'm not surprised at anything really UNLESS something gets fixed without a hitch on the first try... I might be scared if that happens

Lol BUT I have another question for you lads. I got it running which was great and its not running awesome ( as would be expected for not having turned over for a summer-winter-spring ) but it does work however ,now, just after it starts running for a few seconds there is an alarming amount of smoke coming from the rear cylender's exhaust gasket ( where the super small pipe ( the one that is attached directly to the engine) and the exhaust pipe out and down the bike meet). I understand its normal for all the gak to burn off after... almost any maintenance really but I'm worried this might be doing something extra or if I should have coated the gasket with something before re-installing it or....

any words of experience?
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umop-ǝpisdn

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Re: Backfire, timing after rebuild need help!
« Reply #6 on: April 28, 2018, 06:04:07 AM »

Did you connect that pipe to anything? It sounds like the AIS pipe. Its an emissions thing.
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spit051261

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Re: Backfire, timing after rebuild need help!
« Reply #7 on: April 28, 2018, 08:37:25 AM »

Wouldn't this thread be better placed in the GV section rather than Hyosung parts section ?
Just a thought and he may get more help if it was in the relevant section  :)
I suppose we can start posting anything , anywhere now then ? 
Think my place is going to be off road section for everything from now on and at least Cloud will be there to keep me company  ;D
« Last Edit: April 28, 2018, 08:42:12 AM by spit051261 »
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Christianleon266

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Re: Backfire, timing after rebuild need help!
« Reply #8 on: May 30, 2018, 07:50:49 PM »

Like everyone has said, your timing is off, and needs to be corrected. The smoke is probably oil, assuming you used assembly lube when replacing all of your stuff connecting rod onwards, and that cylinder hasn't fired correctly until that point. Make sure your AIS (small pipe protruding from jug that isnt exhaust pipe.) is connected to the AIS valve, or capped off if it is deleted. I would give it a few minutes of running before assuming you have something major that has happened.

If 3-5 minutes pass by of running and you still have buttloads of smoke, I would be eyeballing valve seals or oil rings on the piston, with the latter being more probable.

Don't sweat the mistakes. Everyone makes them, its how you get good at something. When I worked on my virago and my starter bendix gear took a dump, I was nervous at trying to remove the case. Took 3 days to do it due to messing up the arrangement a few times. Now it would probably take 10 minutes to do.
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umop-ǝpisdn

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Re: Backfire, timing after rebuild need help!
« Reply #9 on: June 06, 2018, 10:21:40 AM »

People always blame me for going off topic, but I reckon that if there was a turbocharged forklift, the size of turbo would be awesome for a sleeper 250 and that if there was a turbocharged forklift, Christian would know about it.

Plus, relevant sections are for grammar nazis
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