Engine got louder, what to do?

[Ed Canvasser]

My son and I were on a ride this weekend, and he stopped me to tell me something sounded odd in the engine. Sure enough, the engine was making a much louder then normal sound. It's not necessarily a harsh sound and the motor still runs fine, but it's definitely louder. I've visually looked over the outside of the motor and don't see anything obvious. I thought it may be just an exhaust leak at the head pipe, but unless it's very very small and could make a huge sound difference, then that's not it. Oh ya, the oil level is fine as well. Anybody have any suggestions on other things I could possibly check prior to taking into the dealer?

[300exOH]

Originally posted by Ed Canvasser
My son and I were on a ride this weekend, and he stopped me to tell me something sounded odd in the engine. Sure enough, the engine was making a much louder then normal sound. It's not necessarily a harsh sound and the motor still runs fine, but it's definitely louder. I've visually looked over the outside of the motor and don't see anything obvious. I thought it may be just an exhaust leak at the head pipe, but unless it's very very small and could make a huge sound difference, then that's not it. Oh ya, the oil level is fine as well. Anybody have any suggestions on other things I could possibly check prior to taking into the dealer?

What type of sound is it? A loud ticking could indicate that your valves need adjusted. The gasket where the header meets the head could be bad. If it sounds like the exhaust is louder then you could just need a new copper gasket. Also you may want to inspect the whole exhaust for any holes or leaks. If it has an aftermarket pipe you may just need to repack the silencer.

[Ed Canvasser]

I'm pretty sure it's at the engine, could be head pipe, but not the muffler. Any suggestions on finding out instructions so I can maybe check valves myself, or is this something that the dealer should do. I've done valve adjustment on my Volkswagon Bug many years ago, but never on a quad, as I always have had 2 cycle motors until this one. Thanks again for your help!

[300exOH]

Originally posted by Ed Canvasser
I'm pretty sure it's at the engine, could be head pipe, but not the muffler. Any suggestions on finding out instructions so I can maybe check valves myself, or is this something that the dealer should do. I've done valve adjustment on my Volkswagon Bug many years ago, but never on a quad, as I always have had 2 cycle motors until this one. Thanks again for your help!

Valve adjustment on the 300 is fairly easy. The worst part is removing the plastic and fuel tank but it isn't too bad. All you need to do is remove the round "caps" on the top of the valve cover and use a feeler gauge with a angled end. You can buy the straight ones and bend the end yourself if you can't find angled ones the right size. The gap should be .004" for intake and exhaust. Just loosen the jamb nut on the top of the valve and adjust to spec and tighten the jamb nut and recheck the gap. The feeler should have a slight resisitance but not too tight. This should be done with the engine cold.

[honda300EXtreme]

also make sure your engine is a top dead center,

and i would get a service manual, it will help alot

[Ghost-Rider]

I would definitely check the valves.

[300exOH]

Originally posted by honda300EXtreme
also make sure your engine is a top dead center,

and i would get a service manual, it will help alot

Oops forgot that little detail. :o Sorry about that. I always work from the manual myself simply because I tend to forget things like that. Good advice! I picked mine up off of ebay for about $20 and it was worth every penny.

I'm sure a quick search on here should turn up the exact procedure. If you don't find it I'll look it up in my manual.

[Ed Canvasser]

Thanks a lot guys, much appreciated. Will pick up a service manual and give it a try.

[Ed Canvasser]

Well, I got a service manual and adjusted the valves to .004, but still making the noise. The intake valves were not too bad, but the exhaust valves were way off, I could probably move the rocker a good 1-2 mm. After the adjustment, I would say it is quieter, but still not right and know something is wrong.

Since this noise got louder in a very short time, within a 30 minute ride, I'm suspecting something failed or is in the process of failing. The service manual says to do a leakdown test to check valve problems or piston problems.

Is this is a reliable test, or does it make sense to do at this time or should I take the head off for further inspection?

The exhaust valves were so far out of adjustment that I keep going back to this in my mind... is this a clue to another portion of the valve train that's bad or going bad?

[300exOH]

Originally posted by Ed Canvasser
Well, I got a service manual and adjusted the valves to .004, but still making the noise. The intake valves were not too bad, but the exhaust valves were way off, I could probably move the rocker a good 1-2 mm. After the adjustment, I would say it is quieter, but still not right and know something is wrong.

Since this noise got louder in a very short time, within a 30 minute ride, I'm suspecting something failed or is in the process of failing. The service manual says to do a leakdown test to check valve problems or piston problems.

Is this is a reliable test, or does it make sense to do at this time or should I take the head off for further inspection?

The exhaust valves were so far out of adjustment that I keep going back to this in my mind... is this a clue to another portion of the valve train that's bad or going bad?

It could be a worn cam or even an issue with the valves. If it had been ran for a long period of time with the valves improperly adjusted it could have messed up the cam, valves or maybe even the springs. The leakdown test would let you know the condition of the rings and valves/valve seals but it won't tell you anything about the cam. Have you checked out the timing chain and tensioner? I do know the chain can stretch or the tensioner break and they will make noise and even jump out of time.

[Space Monkey]

I am having the very same problem with my 94 300ex. I rode for a couple of hours the other day and it started to make the same noise in the top end. It was a little low on oil so i put some in and it didn't help any. I adjusted the valve and that didn't help either. My exhaust valves were way off too but the intakes were fine. Someone just suggested to me that i check the timing chain too.

[bwamos]

A leakdown test is a very good test.

You can tell if it is leaking excessivly and usualy where.

If the exhaust valves, you will hear it coming out of the header.
If the intake valves you will hear it come out the intake.
If it's the rings you will hear it come out of the oil fill hole (remove the fill plug).
etc...

It will always leak down slowly past the rings. .but you shouldn't see it leaking past valves, etc..

Cam chain could have also stretched causing it to jump a tooth. Often that will cause blowback through the carb because the intake valves close late.

A very high possiblilty being a 250x. Especially since theres a high chance it's still the stock cam chain. When a chain stretches the distance between the pivots increases because the plates stretch. This firces the chain to ride up higher on the sprocket. Once it stretches a certian distance it can hop up and over the tooth to the next slot.

[Ed Canvasser]

Would seem to me, the head needs to come off regardless so the cam chain, valves, etc. can be inspected. So, is the leakdown test still required or even that helpful if I'm going into the motor either way?

[RichM1983]

I had a 92 250x and it did the exact same thing. It started ticking one day when the oil went low and even after I adjusted the valves the sound stayed. I never figured out the problem and eventually traded it for a quadracer. Good luck I hope you get it figured out.

[300exOH]

Originally posted by Ed Canvasser
Would seem to me, the head needs to come off regardless so the cam chain, valves, etc. can be inspected. So, is the leakdown test still required or even that helpful if I'm going into the motor either way?

I would have to say yes. You don't want to go in there looking for timing chain issues when its actually a valve issue. The leakdown test should at least help you rule out some other possibile casues before you even take anything apart.

[2muchquad]

Being that its hard to troubleshoot anything over the net,i wouldnt be surprised if it wasnt your timing chain.When they stretch they will make a ticking noise from the topend,it will sound like valve train.Remove the timing chain tensioner and try to reinstall it without collapsing the plunger.if it seats almost all the way without doing this then your timing chain is excessively long.i like to see a half inch or so of the tensioner before it bottoms out againt the cylinder.

[Ed Canvasser]

I will do both tests suggested and report back. 1st a leakdown & compression test, 2nd inspect the cam chain tensioner... thanks to all, and i'll be back shortly. Any other comments or ideas, please keep them coming as this is my first venture into a 4 stroke motor.

[dork]

peek in at the cam lobes and see if the hardfacing is coming off. any metal in the oil? do you have oil pressure?

[Space Monkey]

did you ever get the engine apart and see what was wrong?