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Increased backfire/misfire

Old 06-11-2013, 09:14 AM
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Increased backfire/misfire

Hey guys, so recently went thought and changed out my OEM auto CCT's to Krieger Manual CCT's following this guide:

www.vtr1000.org • View topic - Manual Cam Chain Tensioner Installation Guide (MCCT's)

Chain didnt jump any sprockets and i adjusted the CCT's to allow for ~6mm of slack on the chain under the chain guide. I also swapped out my plugs, instead of going with 8's i have 9's and as soon as i started it up and warmed up it seems to have a misfire at idle and a crazy backfire upon deceleration. Is it possible its the plugs completely causing this issue to act up? I will be swapping the old ones back in tonight but would like to know if anyone else has experienced this, maybe i need to loosen up the CCT's an 1/8th of a turn? Any advice is appreciated, thanks.
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Old 06-11-2013, 09:21 AM
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Swap out the plugs. easy way to confirm things.
my thought is one of the cams may be one tooth off. can it rev? or does it back fire spit and cough at around ~5-7k rpm?
that's what I was getting with 1 tooth off.
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Old 06-11-2013, 10:23 AM
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Originally Posted by Caffeine View Post
Swap out the plugs. easy way to confirm things.
my thought is one of the cams may be one tooth off. can it rev? or does it back fire spit and cough at around ~5-7k rpm?
that's what I was getting with 1 tooth off.
I doubt it is off by a tooth, it revs solid up to redline, i took it out for a 55 mile ride to see if it would go away at all and it ran fine through all gears without any issues. Only time it is noticeable is at idle and once i let off the throttle, i'll swap the plugs tonight and report what i find.
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Old 06-11-2013, 02:57 PM
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Originally Posted by bbancsov View Post
Only time it is noticeable is at idle

Symptomatic of a vacuum tube that's disconnected.
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Old 06-11-2013, 04:35 PM
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Originally Posted by zxbud View Post
Symptomatic of a vacuum tube that's disconnected.
Really? I'm certain i had hooked everything back up, even double checked it today when i put the old plugs in. Here's a video of the backfire after throttle, i couldnt get a good one that would how the issue at idle.



I'm guessing the MCCT's are too tight? Should i back them off by an 1/8th of a turn? This is the only thing that has changed.

Last edited by bbancsov; 06-11-2013 at 04:45 PM.
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Old 06-12-2013, 03:50 PM
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I took the tank and airbox to doublecheck all my connections, all were good aside from this one below. It goes to the right side of the front carb and wasnt connected to anything, looks just like a breather line? Any ideas? I have a 2000 mile trip coming up at the end of the month and need to get this thing ready! Any and all help is appreciated.

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Old 06-12-2013, 04:24 PM
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Old 06-12-2013, 05:05 PM
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It goes to the pair valve,if the pair valve has been removed just plug the hose with a screw.
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Old 06-12-2013, 06:30 PM
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Originally Posted by zxbud View Post
Symptomatic of a vacuum tube that's disconnected.
Did anyone else think of this right away?


Sorry, back on topic...
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Old 06-13-2013, 07:45 AM
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I'm going to do the PAIR delete mod this afternoon and see if the afterburn issue is resolved. Am i missing something in regards to that pic??
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Old 06-13-2013, 07:51 AM
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An early version of the iphone used 1,500 vacuum tubes (non Honda) - probably a bit before your time, but it was hi-tech in its day and helped win the war ;-)

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Old 06-13-2013, 01:51 PM
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Did anyone else think of this right away?
Yep I did while reading through the first post.

For future reference an overtingt camchain wont cause a backfire or misfire but the bike would struggle to turn over and you may get a squeaching sound a bit like the sound of a fan belt on a car slipping.

(:-})
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Old 06-13-2013, 07:32 PM
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Originally Posted by Wolverine View Post
Did anyone else think of this right away?




Sorry, back on topic...
Is it a new alien technology? What does it do? Did they find it in Rozwell? It looks dangerous
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Old 06-16-2013, 12:11 PM
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NO change after removing the PAIR system and flipping the reeds. Could this potentially be caused by the CCT's being too tight?
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Old 06-23-2013, 12:35 PM
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Not trying to beat a dead horse here guys but i took a video that better describes the problem. It's the somehwhat "faint" popping sound while at idle, any advice is appreciated i'd like to get it resolved in the next week before i take the bike on a 2000 mile trip! Thanks

video-2013-06-23-15-15-27_zps2e01207c.mp4 Video by bbancsov300 | Photobucket
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Old 06-23-2013, 12:46 PM
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Originally Posted by bbancsov View Post
Not trying to beat a dead horse here guys
Not beating a dead horse at all bb. If I had the knowledge to help you, I would. I would guess cam chain tension wouldn't cause that. I had nothing like it when I swapped mine.
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Old 06-23-2013, 01:02 PM
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Originally Posted by bbancsov View Post
Not trying to beat a dead horse here guys but i took a video that better describes the problem. It's the somehwhat "faint" popping sound while at idle, any advice is appreciated i'd like to get it resolved in the next week before i take the bike on a 2000 mile trip! Thanks

video-2013-06-23-15-15-27_zps2e01207c.mp4 Video by bbancsov300 | Photobucket

It sounds like it's idling too fast and the throttle sync is off. Did you plug that vacuum tube yet? Does it pump 165 psi in each cylinder cold crank pressure? It should sound like this one------

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Old 06-23-2013, 01:05 PM
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Yes i plugged that tube when i did the PAIR removal. Is there a way to resynch the throttle tubes? What baffles me is i didnt touch anything when doing the manual cct installation, and thats all thats changed. Nothing else.
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Old 06-23-2013, 02:05 PM
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It's a Pain

Originally Posted by bbancsov View Post
Yes i plugged that tube when i did the PAIR removal. Is there a way to resynch the throttle tubes? What baffles me is i didnt touch anything when doing the manual cct installation, and thats all thats changed. Nothing else.
I know it's a pain but for logic's sake retrace your steps and pull the valve covers to check cam index marks. Take pics and post them. I bought a 1984 Honda v65 Saber that was hugely torquey and the front intake cam was advanced 1 tooth. It ran very fine and had a lot of miles on it so advancing the intake on the worn cam chain worked well. I don't remember if the rear intake was advanced too but somebody's mistake was a good one. Either there's dirt in the pilot circuit, or there's a vacuum leak or there's a timing mistake in yours.
Only the throttle plates can be synced by turning the sync screw on the left side of the carbs.

Last edited by zxbud; 06-23-2013 at 02:09 PM.
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Old 06-24-2013, 02:38 PM
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There's something not right there. As long as your 100% certain it's not the PAIR/Vacuum system, I agree with zxbud and think you need to remove the cam covers again and verify that it's all OK. When moving from the rear cylinder (cam lobes pointing upwards and inwards) to the front cylinder, were the cam lobes on the front pointing upwards and outwards. It's very easy to not turn the crank over enough and stop the first time that the FT mark lines up which is wrong. This is why I say to remove both cam covers and verify that you are definitely at TDC on the compression stroke by verifying by the position of the cam lobes. CCT tension would not cause that but timing not right will.

You may also want to make sure that you have no air leaks either at the carb inlets or in the exhaust system also, as this will cause a bit of popping and banging.

(:-})
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Old 06-25-2013, 07:32 AM
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I will pull the covers and post pics tonight, thanks for the advice guys.
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