A few weeks ago I posted a message about a strange noise I was getting along with some performance issues.
The problem happened on a ride one day. My bike went from running great to acting as though the idle screw had been adjusted A LOT because it wanted to stall at stop signs/lights. I adjusted to compensate but it still isn't running quite right. Along with this problem there is a *tst, tst, tst* hissing noise in rhythm with the engine.
What I've checked:
Oil level - filled it up the day of the problem
Vaccuum Caps on top of carbs - yep, they're there.
Valve Clearances - checked at the beginning of the riding season - good but on the edge of being tight.
Exhaust Manfild Gaskets - all 4 bolts are tight.
So, any ideas what may be going on?
Thanks - you guys always come through and save my butt!!! :thumb:
i am thinking valve clearnce(spell)
bump
Have you checked for vacuum leaks? Have you checked the timing/timing chain?
Do you hear the noise at (possible elevated) idle? If so, try to locate the source.
I second trying to locate the noise. "Tst tst tst" almost sounds like a vacuum leak of some sort...
I think it's either a vacuum leak, or possibly the intake timing is off.
If the cam somehow is one tooth late (or possibly more) on the intake, then the cylinder would start going down before the valve opened, creating a vacuum. When the valve opened, it would probably cause a hissing sound as the air slipped by. This would also account for the lack of power since the engine must fight against the vacuum and there would be a loss of compression since the valve closes late. I put my money on this one because everyone else is betting on a vacuum leak. However, they both would make a tst tst tst sound since the cylinders are individually carbureted.
If you can't locate the source of the sound, then check the timing (see the Clymer manual). If it's off, check the condition of the cam sprocket teeth, the cam chain tensioner, and the cam chain. If it's not off, then there has to be a vacuum leak somewhere.
Awesome, thanks for all the help.
This may be useful. When it started acting up I remember hearing what sounded like a stick breaking. However I dismissed it because I was in stop and go traffic and figured that someone just ran over something causing the noise. Maybe something snapped in the top part of the engine? I suppose I'll know more once I take it apart.
I REALLY didn't want to have to do that. It seems like I just got the stupid thing back together. One of these days I'll have to count my losses and look for a bike with less problems! :icon_rolleyes:
Quote from: stephan on July 31, 2006, 08:10:13 PM
This may be useful. When it started acting up I remember hearing what sounded like a stick breaking.
That could very well have been the intake cam slipping a notch. The only thing you have to do to check the timing is take off the valve cover and the contact cover and count links in the chain. To get to the tensioner, you probably will have to take off the carbs. My guess is that the tensioner is malfunctioning (possibly broken spring) or that the cam chain is worn out (unlikely unless it's high mileage or worked very hard).
Snapping, ticking sounds make me think electrical arcs/arcing. If this bike has ever been left outside, the HV lead from each coil could be breaking down. This would definitely cause rough running.
Few people realize that there are several thousand volts carried by the wires and if the insulation has been exposed to UV (sunlight) for a sufficiently long period, it breaks down the rubber/plastic of the wire.
It doesn't need to be exposed to sunlight to breakdown either. A cleaner or solvent can do the same thing. Moisture intrusion in the wire can cause a breakdown also.
This electrical system was not designed for enduro use. High pressure hose washing will intrude the high tension (HT or HV for another term) wiring also.
Now you have another vector to chase! :) Pick up a cheap mechanics stethescope -- the kind with the removable rod -- and use the tube end to sniff around the engine for the source of the noise.
Intersting - I never thought about an electrical issue . . . :dunno_white:
Regarding the cam chain and tensioner, both are the originals and the bike has about 19,000 miles on it. I've only put about 4,000 miles on it and haven't driven it THAT hard. However who knows about the previous owners . . . Is there a way to know if the tensioner if bad? Would a slipped cam chain pretty much answer that question? Now for the scary part - how much is a new tensioner? :o
Nevermind - found it on Bike Bandit - $50 plus shipping. If that's the problem that's not too bad.
I'll have to pull the tank and do some checking this week for what's going on.
Thanks soooooooo much for all the suggestions. I'll post an update when I know more - THANKS!!! :thumb:
Your problem could be something as simple a loose sparkplug. Check both are tight in the head before you go diving in. A loose plug will give the exact same symptons you describe.
I was sure I posted something about loose plugs to this thread earlier.
I guess I forgot to hit post or something?
Brilliant idea! But unfortunately not the case. I just checked both plugs and they're nice and snug - dang! I love it when the simplest answers are what's wrong! No deal this time. ;)
I'm really leaning towards the vavle issue rather than an intake issue. When the problem started my bike wanted to idle so slow it would stall. A leaky intake should cause the idle to increase from what I understand. From what I can tell with my head next to the engine the sound is coming from the upper front of the engine. The bike runs okay, albeit rough. I can hear the *tst, tst, tst* sound all the way until the motor stops and the last piston stops which leads me to believe it's a valve problem.
How does a cam chain slip? Does that tell me for sure that the tensioner is bad? The bike is rideable, will this cause any problems such as bent valves, etc?
Thanks guys - this place, as always, is a wealth of knowledge!
You guys rock!!!! :thumb:
If the cam chain slips, then it tells you for sure that the tension is insufficient. this could be due to the cam chain or the tensioner. The easiest way to check the tensioner is to take it out. Get a small flat-head screwdriver and put it in and crank the tensioner. It has a coil spring (similar to a tape measure) that is under pressure and should resist. When you take the screwdriver off, it should spring back to fully extended. This pressure is what automatically adjusts the chain tension.
*If* what I said is correct, then the bike is rideable without worrying about bent valves. I don't know what other issues might arise, though.
Quote from: Egaeus on August 01, 2006, 08:49:38 PM
*If* what I said is correct, then the bike is rideable without worrying about bent valves. I don't know what other issues might arise, though.
That's it - I'm holding you to that!!! :laugh:
Okay I'll check this bad boy out tomorrow night and see what I come up with. I'll post an update when I know more.
If the timing is off I'll order me up a tensioner, if not I'll check it out for any leaks or vacuum issues. :thumb:
Thanks again!
Problem solved!!!! :)
It turned out to be an uncapped vaccum on the side of one of the carbs. I was able to remove the gas tank and start it with the rest of the fuel in the hoses, find the noise and when I put my finger over the hole - poof!!!
It was like someone waved a magic wand to make it purr like a kitten. So I capped it off, put everything back together and went for a spin. Runs great again - yesssssss! :thumb:
Thanks everyone for your help! I can't tell you how happy I am that I didn't have to remove the valve cover and check the valves. I would've, but am gald I didn't have to!
THANKS AGAIN!!! :icon_mrgreen: