75 860GT Engine Noise--

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JD
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75 860GT Engine Noise--

Post by JD » Mon Aug 16, 2010 10:42 am

I let my brother ride my 75 860 this last weekend. He pointed out a noise that I either had'nt heard or just ignored in the past. It is a slight rattle noise with the engine in gear, under a load and is most pronounced under 3500 rpms. The bike runs out wonderful. Starts first kick, no smoke and no noises when in neutral, even with a crisp twist of the throttle. I've only owned it for a year or so, and have only put just over 1000 of the 37k on the clock. I've changed the oil and filters. I have not, however adjusted the valves as of yet. I took the bike on a 100 mile ride yesterday and that noise is all I hear now! No vibration, no unusual feedback from the chassis that would indicate anything making unusual contact with anything else. The hard part is isolating the noise, because it only happens when its moving. I didnt hear any noise while at a stop light in first gear, even with feathering the clutch. Any thoughts? Thanks in advance.
JD
1969 Norton Commando S
1972 Norton Combat Commando
1958 Bianchi Tonale
1959 Gilera 150 Sport
1948 Indian Scout
1977 Ducati 900 GTS
1978 Honda XL250s

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Steve Foster
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Post by Steve Foster » Mon Aug 16, 2010 3:56 pm

JD - it could be "pinging". A Google search will reveal some of the possible causes - low octane fuel, lean mixture, ignition advanced, engine overheating, carbon build up. Because engines only ping when under load you won't hear it when you are stopped or feathering the clutch.

Steve.
1974 Ducati 750 GT

mizike77
860 GT / GTS
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Post by mizike77 » Tue Aug 17, 2010 3:57 am

Is your chain rubbing on your swingarm/engine cases?
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baddean
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Post by baddean » Tue Aug 17, 2010 5:20 pm

Center bolt on clutch basket loosening? Was somewhat common on the roundcases.
Could explain noise under load and no noise at idle. But will get noisier the more it loosens.
As has been said already, could be your drive chain be contacting the engine case.
Steve has a cure for that with the case savers.
Broken spokes in the wheels?
When you hear the rattle while riding pull in the clutch to see if the rattle is in the chassis or the engine. If you let the engine drop to idle while moving and you have a rattle then it is not the engine. Does the rattle increase and decrease in intensity based on engine revs?
Does it just rattle the same no matter what the engine revs?
Center stand bumper gone allowing it to rattle. Muffler, gas tank?
Just throwing things out there to see if maybe something will stick,
Let us know,
Dean
Faster, faster until the thrill of speed overcomes the fear of death.
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Lumpy
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rattle

Post by Lumpy » Thu Aug 19, 2010 4:23 am

Does it have the electric start mechanism on it?? Maybe try removing the chain on the elec start and going for a spin. A mate of mine had a strange rattle coming from his 860 GTS and it was due to the chain and sprag bisso in there.

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JD
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Post by JD » Thu Aug 19, 2010 9:43 am

Thanks all for your help. I managed to check it out yesterday, briefly. I pulled the plugs to see if it seemed lean...nope. Plugs are just on the darker side of chocolatey brown. I rode it for a bit to see if it was chain noise hitting the case. Not that either. When I pulled the clutch in, the noise would stop instantly. I have some spare gaskets that I bought from Steve a while back. I am going to pull the clutch cover and see if the basket is loose. I am also going to drain the oil and change the filter again, since it's due. I'll see what comes out then. Hopefully nothing. And since I do not have an E-start bike, that eliminates several other possibilities. Thanks again for all the help. This noise concerns me a bit. I own and operate an automotive repair shop--different, I know from bikes, but when a car comes in and rattles like this bike does, it usually means get off your wallet and spend some $$$. Cheers.

JD
1969 Norton Commando S
1972 Norton Combat Commando
1958 Bianchi Tonale
1959 Gilera 150 Sport
1948 Indian Scout
1977 Ducati 900 GTS
1978 Honda XL250s

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BevHevSteve
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Post by BevHevSteve » Thu Aug 19, 2010 9:57 am

Hey JD it could be just as simple as your clutch cable is too loose so the clutch actuator rod is vibrating around and hitting the cover. Reach down and give it a wiggle.... Can it hit the cover? If it can, it needs to be adjusted [the adjuster at the center of the clutch basket]
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JD
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Post by JD » Thu Aug 19, 2010 10:24 am

Thanks Steve. I hope it is as simple as that. I love riding that bike, and though I have several others, this is the one I always default to. I'll keep us all up-to-date on any news.

Cheers.

JD
1969 Norton Commando S
1972 Norton Combat Commando
1958 Bianchi Tonale
1959 Gilera 150 Sport
1948 Indian Scout
1977 Ducati 900 GTS
1978 Honda XL250s

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BevHevSteve
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Post by BevHevSteve » Thu Aug 19, 2010 10:38 am

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JD
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Post by JD » Thu Aug 19, 2010 3:33 pm

OK--I brought the bike to my shop to do some more exploratory work. I pulled the clutch cover and removed the clutch plates. Clutch basket is rock solid. More good news, the clutch looks brand new. Still has the branding on the friction plates. I removed the alternator cover and shifter cover. This is where some bevel head pros need to advise-- I pulled the spark plugs out and reinstalled the kick start lever and spun the engine. On the bearing plate there are 2 bearings. When I spun the engine around, only the bearing and shaft on the VERTICAL cylinder would spin. The HORIZONTAL bearing and shaft would not. The bevel gears were still turning, obviously, since the bike runs very well. What is the shaft that is behind those gears? Doesnt sound very promising whatever it is. Thanks again in advance.

JD
1969 Norton Commando S
1972 Norton Combat Commando
1958 Bianchi Tonale
1959 Gilera 150 Sport
1948 Indian Scout
1977 Ducati 900 GTS
1978 Honda XL250s

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JD
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Location: Bakersfield, Ca

Post by JD » Thu Aug 19, 2010 5:03 pm

Scratch that last issue-- I pulled the bearing plate and gears out. The bearing is not seized, it just needed to be seated straighter. It was only slightly binding, as I loosened the corner nearest to the horizontal bearing, it freed up and started to spin. Im learning a bit of history as I go along. Looks like it's been into pretty deeply in the past.

JD
1969 Norton Commando S
1972 Norton Combat Commando
1958 Bianchi Tonale
1959 Gilera 150 Sport
1948 Indian Scout
1977 Ducati 900 GTS
1978 Honda XL250s

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JD
Mariana
Posts: 40
Joined: Thu Oct 30, 2008 10:23 pm
Location: Bakersfield, Ca

Post by JD » Sat Aug 21, 2010 1:53 pm

Alright, engine's all back together and running. Fixed a small oil leak in the process. I was able to isolate the noise positively to the clutch side. It will make the rattle noise for a split second now when blipping the throttle. My question now is could this be a mid-range throttle issue? Or, do I need to go back into the clutch cover and do a bit more looking? Anything else prone to being noisey on that side? Thanks again for all the help.

JD
1969 Norton Commando S
1972 Norton Combat Commando
1958 Bianchi Tonale
1959 Gilera 150 Sport
1948 Indian Scout
1977 Ducati 900 GTS
1978 Honda XL250s

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