Author Topic: Low RPM clicking??? (Read 4564 times)

Lumbee · « **on:** March 28, 2006, 08:40:02 AM »

...I just brought a 77 750F back to life the last few months. Finally got the carbs cleaned (3rd time is a charm

) and starting to put a few mines on it. I put new oil in it, and set the valves this past weekend, however I'm getting some disconcerting noise from the head at low RPMs. It happens like this. If I'm accelerating, and I start from a higher gear, so I'm around 2K rpm, and get on the throttle, for a few seconds I hear was sounds like valve lash (clicking sounds) coming from the head. With in a second or 2 as the RPMs increase the noise goes away. As I said I adjusted the valves, so I'm fairly confident they are set correctly. Any ideas on what this is?

This bike is to be my "cruiser", and I've got the barn door windjammer farring on the front, so I'm hoping the clicking is just some of the harware up front thats banging against something, though I can't find anything that is loose.

...any ideas or comments appreciated...

SteveD CB500F · « **Reply #1 on:** March 28, 2006, 08:58:41 AM »

If you are in a high gear and load up the engine - this couldn't be pinking / pre-ignition / detonation (delete depending upon location) could it?

Timing out or crap fuel (?)

hcritz · « **Reply #2 on:** March 28, 2006, 09:04:15 AM »

Yep...sounds like pre-ignition...
Try a tank of premium...gas ain't what it used to be in 1977!

eldar · « **Reply #3 on:** March 28, 2006, 09:16:48 AM »

You should not need premium. It is a waste. these bikes, if they are stock, will not gain anything using premium. However, if you try it and the ping goes away, you know your timing is off.

Lumbee · « **Reply #4 on:** March 28, 2006, 09:22:52 AM »

...pre-ignition?? ...not familiar with the term/concept...someone give me a quick primer... $:-\$

...and just so you know, the bike doesn't cut out or seem to run bad at the lower RPM's...just the clicking...no bogging down...

hcritz · « **Reply #5 on:** March 28, 2006, 09:31:37 AM »

Pre-ignition is when the fuel burns too quickly...explodes instead of burns...causing a knock...can be caused by timing set too high...fuel with too low an octane...even a hot spot in the combustion chamber (carbon deposits etc.) If it is excessive it can damage the engine. Modern cars actually have knock sensors (little microphones) that listen for pinging and electronically adjust timing accordingly...some are sophisticated enough to do it per cylinder.
I was just looking at the 77 manual it says use a pump octane of 86 or higher...and that unleaded fuel is NOT recommended!
Well...not much we can do about the no lead!
If you try a tank of premium and the rattle goes away...check the timing.
I just use premium...for the small amount of fuel that it uses...really doesn't cost much in the whole scheme of things and usually they have better additives for keeping things clean...

eldar · « **Reply #6 on:** March 28, 2006, 09:53:07 AM »

The higher octane fuels create more heat during their burn process. This has been one of those topics that has beaten so much it is past dead. Kinda like the "what oil do you use" topic.

my78k · « **Reply #7 on:** March 28, 2006, 10:04:01 AM »

Could using either too cold or too hot of a spark plug contribute to this? Or would that be felt at all RPM ranges...

eldar · « **Reply #8 on:** March 28, 2006, 10:21:02 AM »

maybe too cold of a plug but I dont think so. Never seen that happen anyways.

hcritz · « **Reply #9 on:** March 28, 2006, 10:32:08 AM »

I doubt that a cold plug would...and if it's in the recommended heat range for the engine...probably not.
With aircooled car engines some interesting things can happen...If you get a spark plug that extends too far into the combustion chamber...one or two too many thread...or not using the washer on the plug...it can cause a hot spot and cause pre-ignition.
I'll have to read up on the higher temps on premium fuel burns...except at high throttle settings I don't think it would make much difference...there are a lot of issues with flame speed and shape etc.
I have an EGT (exhaust gas Temp) sensor and a cyl. head temp on my air cooled sypder...it's similar in compression etc...
would be interesting to see what those gauges show with a tank of reg vs prem. It is definitely more prone to pinging with regular!
It was designed to be run on leaded fuel as well...so it's a bit octane sensitive...of course when these bikes were built...octane ratings for most premium was a lot higher...The Spyder's owner's manual says use 100 octane...Yeah Right!!!

eldar · « **Reply #10 on:** March 28, 2006, 10:37:23 AM »

some engine do require the higher octane but wehave low enough comp that unless you use an 836 kit, you should not need it as long as everything is tuned right. No I think his ping is mechanical. maybe adjust the cam chain and then recheck the valves lash.

Lumbee · « **Reply #11 on:** March 28, 2006, 10:51:34 AM »

...def sounds mechanical to me. I've already adjusted the cam chain, and I know the valves are set, however I'v only statically adjusted the timing. Sounds like a good excuse to finally get that timing light!!!

my78k · « **Reply #12 on:** March 28, 2006, 11:02:37 AM »

See that's part of the reason I am always broke...I don't wait for an excuse to buy tools

hcritz · « **Reply #13 on:** March 28, 2006, 11:05:23 AM »

Yep...hard to diagnose a noise from a post!<G> But under load...sounds like pre-ignition.
Be a good idea to recheck alll the tuneup stuff...a lean carb could also contribute as well.
Not sure with my helmet on I could hear pinging???

Being an engineer and a Geek....you have me interested in the burn temps with different octanes...logically the better control burn of higer octane would give a cooler burn...but there are lots of other factors too.
I notice the compression ratio of the stock motor is 9.2/1 not exactly low for a non-injected/non-computer controlled engine. + the higer temps that aircooled ones run...also the typical RPM that these engines run at hwy speeds it higher than most...
So...my interest if peaked!

Bob Wessner · « **Reply #14 on:** March 28, 2006, 11:08:01 AM »

Quote

Yep...hard to diagnose a noise from a post!<

Along these lines, some digital cams allow you to capture a few seconds of sound. Any chance you could to that and post it?

Lumbee · « **Reply #15 on:** March 28, 2006, 11:14:31 AM »

Quote

Not sure with my helmet on I could hear pinging???

...noticed the noise when I was wearing my "novelty" chopper helmet, so nothing over my ears...

Quote

some digital cams allow you to capture a few seconds of sound. Any chance you could to that and post it?

...I've been meaning to check this out...my dig. camera does movies...but not sure if it has sound or not. Either way, I'd need to be driving it to make it happen...might be hard to juggle the throttle and holding the camera close to the head at the same time. But hey...I'll check my camera out, if it does sound I might give it a whirl...

Bob Wessner · « **Reply #16 on:** March 28, 2006, 11:17:58 AM »

Quote

might be hard to juggle the throttle and holding the camer close to the head at the same time

Scratch that idea, we would rather have you still be around trying to figure it out.

eldar · « **Reply #17 on:** March 28, 2006, 11:18:47 AM »

any chance it could be points making noise? I would not htink so but saome claim to like the sound of points

cben750f0 · « **Reply #18 on:** March 28, 2006, 11:20:21 AM »

i know for a fact that the big bore kits will ping like a bastard, if you have the timeing even slightly out... so i would get a light and double check that.... just a though... you dont happen to have a valve with a rocker gap slightly too big?... i know when i was getting uses to setting the valves that i set one maybe a 1/2 a thou too big.... that made a racket also.
keep us up with the progress...peace

BobbyR · « **Reply #19 on:** March 28, 2006, 11:42:31 AM »

I have had the same sound on steep hills in too high a gear. It is detonation from applying load in too high a gearat too low and RPM. These motors fool you into not shifting down at proper times since they never seem to complain much.

hcritz · « **Reply #20 on:** March 28, 2006, 12:04:59 PM »

Good Point Bobby...seems these engines like to rev...
Still hurts me to see the tach at 5000 rpm for any distance!<G>

eldar · « **Reply #21 on:** March 28, 2006, 12:15:47 PM »

I know, I hate being at high rpm in town! drives me nuts!

crazypj · « **Reply #22 on:** March 28, 2006, 04:17:48 PM »

Check the ATD isnt stuck at full advance. Check the advancer springs are not broken. they may be allowing full advance too soon if they are weak.need a timing light to verify.
BTW race fuel burns slower. Only creates more heat if you get more air with it or higher compression or both. all gasoline has about 19,000 btu/***/*** energy, ( forgot the next bit)
I'll have to look up specs now I started on this
PJ

BobbyR · « **Reply #23 on:** March 28, 2006, 07:17:19 PM »

If I read the post properly he was coming off 2K Rpm and accelerating quickly. I personally do not like revs myself. I keep my motor around 3K around Town. I want some engine braking for control and the ability to get on it quickly to avoid idiots. 3K is where the real power band begins. These bikes don't buck like cars for some reason so you find yourself getting up into higher gears without thinking. Hell, with the price of gas I may take up coasting.

kpier883 · « **Reply #24 on:** March 28, 2006, 08:15:48 PM »

Could be valves pinging. My 82 KZ1000 used to do that with the fairing installed but not without it. The timing was set too far advanced (though correct by the manual) for the extra drag. At higher rpm the problem was not present. A passenger always made this condition worse on that bike.

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Author Topic: Low RPM clicking??? (Read 4564 times)

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