Author Topic: Poor Running, Loud B4 - Cam Chain Issue  (Read 4056 times)

Offline PitterB4

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Poor Running, Loud B4 - Cam Chain Issue
« on: March 11, 2005, 10:29:19 PM »
Pooly running, loud B4 - Cam Chain Issue
(9/22/03 12:38 pm)
Nobody can figure this out, help!

Alright, heres whats going on. I have a '91 B400 with only 9,974 miles on it. My 1st streetbike. So far its been a great bike, I've got clipons and I can beat my buddy's FZR-1000 in the twisties, a fact that my friend doesnt like one bit coming from a little 400.
Getting to the point, on saturday we tore down my bike and pulled the carbs off because it wasnt revving past or pulling past 12,000rpm. I figured I had a jet clogged somewhere. Pulled the carbs all apart and cleaned them. Stuck them back on the bike. Bike started just fine. I took it a few blocks and came back to put my helmet and armour on because we were going to go for a ride. Everything seemed just fine with my bike as I shut off the engine.
After me and my two friends were all dressed and ready for a nice run up twisty highway 299 up here in northern california, I went to start my bike and it threw what seemed to be a temper tantrum.
The best way to describe this, well, here is what it's doing. When I CAN get it running, I have to tickle the throttle alot to keep it running. The engine REFUSES to go any higher than 1,000rpm. It makes a horrible knocking sound at the same time. The engine ISNT happy for some reason.
What hapened here, because this makes absolutely NO sense to me. Bike running absolutely fine untill I shut it off. I made NO other alterations to the bike after I shut it off. I just moved the engine run switch to off to kill the engine and I got off. When I came back to it maybe 5-8 minutes later to start it, the problem started.
I spent the entire day yesterday going through the carbs. I completly took them apart again to make sure I hadnt missed anything. I have new spark plugs and they are properly gapped. I pulled the #4 sparkplug and it had spark. I'm not sure about the others, but tonight I'm going to pull them and make sure theyre all getting spark.
I'm also going to pull the petcock vacuum line and make sure nothing's stopping it up. I just done get this.

ONE OTHER IDEA we had is perhaps one of us knocked off a hose that conects the top of the carbs together. It seems that theres an opening on the #2 and #3 carbs that if I tilt the carbs, gas will puke out. Shouldnt they be bridged together with some hose?

PLEASE PLEASE PLEASE help me I'm totally  when I should be  ... The bikes really a great performer and will take my friend's '89 Katana 600 up to about 90mph and outcorner the snot out of him.

Please help, the bandit's also my only means of transportation for now. Thanks!

(9/23/03 2:00 am)
Re: Nobody can figure this out,help!

Check the other 3 cylinders for spark. (Ignition woes are the B4's #1 problem.)
Is there any chance some carb cleaner was left in the carbs?
Did you blow out every passage in the carbs with compressed air?
Not only check the petcock vacuum line (putting it in "Prime" would bypass this though), but you might want to pull the petcock and make sure you don't have anything obstructing fuel outflow.

Maybe one of the B4 owners can help you with hose routing...

Paul W

(9/23/03 12:35 pm)

Last night I checked the spark on all 4 wires, and it's fine. I checked the fuel and vacuum line, no problems evident. After anouthe 2 hours of checking everything I can possibly think of, I'm still  

Since it was running just fine, then I shut it off, then started it back up and the problem arose, I'm thinking it's probably electrical....
Last night I got the bike to run again, only a little better with no valve tapping, however theres a knock and the carbs are intermittantly backfiring. This is why I'm smelling a timing problem. How do I check the timing, and why would it have just gone out of whack like this?

I'm pretty sure after tearing the carbs apart 3 times now that they are clean as a whistle, and it's getting fuel...I'm just thinking its a ignition timing issue.

My cousin supposedly has a manual for the bike but hes in the middle of moving and wont be able to find it for me for another 2 weeks or so... Please help me figure this one out, and if anyone can sum up how to check and adjust the timing on this thing, then it would be MUCH appreciated.

(9/23/03 12:53 pm)
Re: pisser...

What comes to my mind is timing, either ignition or cam. Since this all started when the engine was turned off I think the cam chain has jumped . I would pull off the timing cover and check the timing marks.


(9/23/03 2:20 pm)
doesnt make sense...

How and why would the timing chain jump? This bike has less than 10k miles on DID have too much oil in it though, about a quart over...could that have caused the chain to slip?
(9/23/03 10:29 pm)
May be a dumb question...

...but did you take the time to balance the carbs after rebuilding them? Unbalanced carbs will cause the bike to run piss poor. As for the extra oil, wow, an extra quart is a lot. I would drain some of that out. If the oil level is too high, the crankshaft counterweights can whip up your oil and cause it to foam.

(9/23/03 10:30 pm)
oh and...

...I highly, highly, highly doubt that the cam chain would've jumped.

(9/24/03 11:00 pm)
I didnt "rebuild" them...

I didnt do anything more than clean out the carb's tops and bottoms, and blow air and cleaner through the jets I could find... I dont think I'd have to rebalance the carbs after that.

(9/24/03 11:04 pm)

Dont forget that it was running fine after the carb cleaning, it just started throwing the tantrum after it was running fine 5 mins before that. Weird huh?

(9/25/03 12:36 am)
Yeah, it is weird

That is very weird. I wouldn't look too much at electrical as everything was running fine and it doesn't seem you did anything to cause damage to the electrical. Your bike sounds a lot like mine when it was having carb troubles. Did you tear them down completely? What kind of shape were the o-rings in? I can't help but think it's still a carb issue. I tried cleaning mine out once and the bike still ran pretty bad, so I took them to a shop for a once over. They replaced the o-rings, cleaned them out again, and reassembled them. I installed the carbs on the bike and balanced them and it ran like a dream. Good luck, I know the frustration.


(9/25/03 10:20 pm)

Tore the bke apart tonight... timing was off by atleast 3-4 teeth...but the chain is really tight. I guess running too much oil does wacky things.

Hopefully I didnt mash up any valves....but the bike has compression so I'm thinking that things might be ok. We'll be buttoning it up tomorrow and see how it goes.

Cross yer fingers.

(9/26/03 1:22 am)
Fingers crossed

Wow, off by three or four teeth, that's amazing. Best of luck to you. Let us know how it goes.

I just got my bike back from the shop today so I'm hoping to hit the canyons this weekend (except it's supposed to be hot down here).

(9/26/03 12:41 pm)
Re: Nobody can figure this out, help!

"...I highly, highly, highly doubt that the cam chain would've jumped." hey killer hows crow pie taste lol  
I have been racing Suzuki's for longer than i want to remember and a common problem with them at high rpm is the automatic chain adjuster! If the chain is going to jump it normally will do this when the engine is shut off. This is common to most vehicles. I would check the tensioner and make sure everything is ok. I dought the oil had anything to do with the chain jumping.

(9/26/03 2:01 pm)
Would prefer apple pie.

It would taste better with one of these  

Hey, at least I didn't add any more highly's to that, don't you think?

I have 12 thousand miles on my B4 and do a lot of mountain riding keeping it at high rpm to carve the canyons and have never had an issue with my cam chain. Considering he had just been working on carbs, reason pointed more toward a carb issue. But hey, reason isn't always the right answer, as in this case.

My question is, how does a cam chain jump when the engine is off?  
(9/26/03 4:51 pm)
Re: Would prefer apple pie.

When you turn off the engine and as it slows down just before it stops turning over they tend to kick over backwards, if there are any issues with the tensoiner this is when the chain jumps. Hope this helps

The one armed Bandit
(9/26/03 6:39 pm)
What about the tensioner

My EX 500 used to make a heck of a racket until I put on an improver late model cam chain tensioner redesigned by Kawasaki. It quited the engine while making more power. I have read in magazines like Roadracing World of special "racing" cam chain tensioners that can be adjusted manually. I do not recall any previous posts on weak tensioners but you might have a look at yours to see if the ratcheting mechanism doesn't have too much play or is extending the way it should. Glad to hear everything worked out well for you.
'93 Bandit 400 - SOLD
'98 Honda F3 Track Bike - SOLD
'98 Kawi ZX-6R Street Bike - SOLD
'00 Gary Fisher Kaitai
'09 Bianchi Via Nirone 7