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Loud metal on metal noise under acceleration

Started by Tools99, November 05, 2021, 03:51:52 AM

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Tools99

Got my 85 FJ1100 out on the road today for the first time since buying it. Restored all master cylinders and slave cylinder rebuilt, all fluids changed and carbs rebuilt, new plugs etc. idles great, pulls clean with plenty of power, but loud clacking noise upon acceleration like a mini jack hammer is the best way I can describe it. Definitely metal on metal seemingly each rotation of at least one piston. any ideas?
Timing chain..? Valves? - Nipped up the header bolts so I'm confident it's not that.

Motofun

This will sound weird but it happened to me.  The '85 FJ has double walled exhaust pipes that are prone to internal rusting.  The internal pipe can separate and it then bangs against the external pipe.  I thought I had a rod knock.
'69 Honda Trail 90
'75 Honda CB400F
'85 Yamaha RZ350
'85 Yamaha FJ1100
'89 Yamaha FJ1200
'09 Yamaha 125 Zuma
'09 Kawasaki KZ110 (grand kids)
'13 Suzuki GSXR 750 (track)
'14 Yamaha FZ-09
'18 Suzuki GSXR 1000R (track)
'23 Yamaha Tenere 7
SOLD: CBX,RZ500,Ninja 650,CB400F,V45 Sabre,CB700SC,R1

ribbert

Quote from: Tools99 on November 05, 2021, 03:51:52 AM
Got my 85 FJ1100 out on the road today for the first time since buying it. Restored all master cylinders and slave cylinder rebuilt, all fluids changed and carbs rebuilt, new plugs etc. idles great, pulls clean with plenty of power, but loud clacking noise upon acceleration like a mini jack hammer is the best way I can describe it. Definitely metal on metal seemingly each rotation of at least one piston. any ideas?
Timing chain..? Valves? - Nipped up the header bolts so I'm confident it's not that.

Well, from your description I would have said start by checking the header bolts, but you've done that. A leak there would fit your description, clacking sounding, consistent with one cylinder per cycle and noise relative to load.

I know you nipped up the header bolts but seeing how it was there on the first ride, is it possible there's a flange gasket missing from one cylinder or it's pulled in crooked?

Noel
"Tell a wise man something he doesn't know and he'll thank you, tell a fool something he doesn't know and he'll abuse you"

FJmonkey

The 84/85 header pipes are double walled. When one separates, it sounds like a major internal engine failure.
The glass is not half full, it was engineered with a 2X safety factor.

'86 Ambulance - Bent frame, cracked case, due for an overhaul
'89 Stormy Blue - Suits my Dark Side

T Legg

I think the valves would be a good thing to check . You should also check your ignition rotor and make sure it isn't hitting the trigger coils .
T Legg

Pat Conlon

Yep, also happened to me on my '84....the inner wall on my header tube cracked and started flopping around....sounds like hell.  It seems as though all the 84/85 FJ's will eventually suffer this fate.

Good news, all the single wall 1986 to 1995 FJ header tubes are interchangeable (plug and play) and they are stainless steel so they polish up nicely. If you buy a set of 4 make sure they are a set. On the bottom, the header tubes are stamped with numbers 1 thru 4 to correspond to the cylinders they serve. They are not interchangeable between cylinders.

Cheers.   Pat

1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

Old Rider

If it is the inner tube that has loosened you can fix it by drilling a hole and insert a pop nail .I did that on the 1100 i had before

Tools99

This bike was bought with a 4into1 system.
Would this issue still occur in that case?
I know this issue was with the stock system...

Pat Conlon

Nope, the 4 into 1 system is single wall. Check to see if the header tubes are loose.
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3