Author Topic: Stuck camchain: 750F  (Read 81 times)

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Offline 01Thomas

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Stuck camchain: 750F
« on: March 16, 2025, 11:51:03 AM »
Hi
I'm doing a top-end overhaul of my 1977 CB750F with the engine in the frame and I seek help:
I stripped the engine down to the base gasket and now that I'm assembling it, it turns out that the camchain is no longer around the crankshaft sprocket but has somehow managed to wedge itself between the sprocket and the crankcase. Effectively I've now got a friction-driven camchain.

I can remove the camshaft quite easily and that'll give me plenty of slack but that alone is not enough to free the camchain.

Has this ever happened to anyone else?
Besides removing the engine and splitting the cases, is there anything else I can do to fix this problem?

regards
Thomas
1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Offline Don R

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Re: Stuck camchain: 750F
« Reply #1 on: March 16, 2025, 11:58:28 AM »
 I'd think removing the tensioner and cam would allow enough slack to do a little fiddling and get it back over the gear. Maybe a piece of welding wire or other straight thin tool would help guide it back on. Have you looked through bottom of the case with the pan removed?
 These are ideas not proven techniques, I'm sure someone can say which might work best.
No matter how many times you paint over a shadow, it's still there.
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Offline 01Thomas

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Re: Stuck camchain: 750F
« Reply #2 on: March 16, 2025, 12:12:36 PM »
HI
I can _just_ see it if I remove the oil pan and position my head such that oil drips into my nose but it's impossible to get my fingers in there. I'll try with a piece if wire - wish me luck!
1971 Honda CB750 Four K1 [Engine: CB750E-1113521 / Frame: CB750-1113838]
1977 Seeley Honda CB750F (F1) [Engine: CB750E-2551214 / Frame No: SH7-655F]

'96 Yamaha YZF750SP & '81 Moto Guzzi SP1000 & '80 Moto Guzzi 850 LeMans II & '82 Bimota KB-3 [Frame No 49] & '66 Ducati 50 SL/1 & '53 Miele K-50 & '38 Miele 98

Online bryanj

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Re: Stuck camchain: 750F
« Reply #3 on: March 16, 2025, 12:18:12 PM »
If it fell off it can fall back on!

Been there done that admidtedley with engine on bench , it is a fiddle  but can be done
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Offline BenelliSEI

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Re: Stuck camchain: 750F
« Reply #4 on: March 16, 2025, 02:10:06 PM »
Do you have to remove the cam? With the gear removed the chain should come off the top, leaving enough slack to reset the bottom? Never actually done this, so like Don, just guessing.

Offline HondaMan

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Re: Stuck camchain: 750F
« Reply #5 on: March 16, 2025, 03:08:27 PM »
I'd think removing the tensioner and cam would allow enough slack to do a little fiddling and get it back over the gear. Maybe a piece of welding wire or other straight thin tool would help guide it back on. Have you looked through bottom of the case with the pan removed?
 These are ideas not proven techniques, I'm sure someone can say which might work best.

I've done it that way, many times. :)
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Offline Ozzybud

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Re: Stuck camchain: 750F
« Reply #6 on: March 16, 2025, 03:31:02 PM »
I didn't think you could even remove the valve cover with the engIne still in the frame let alone do a head rebuild?
Is this just true on earlier models? Speaking of 750 SOHC bikes
« Last Edit: March 16, 2025, 03:32:43 PM by Ozzybud »
1976 Z50A YELLOW
1970 CT70 BLUE
1971 CT70H ORANGE
1972 CT70H GREEN
1973 CL200 BLUE
1973 CB350F RED
1975 CB360T RED
1975 CB400F BLUE
1975 CB550 ORANGE
1976 CB750F RED

Offline scottly

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Re: Stuck camchain: 750F
« Reply #7 on: March 16, 2025, 03:36:09 PM »
Thomas has a Seeley frame, which allows the top end removal. :D
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Offline Don R

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Re: Stuck camchain: 750F
« Reply #8 on: March 16, 2025, 05:42:09 PM »
Thomas has a Seeley frame, which allows the top end removal. :D
Is that called a Seeley Sneak? On my big shelf I have an Egli frame that the head can come off in frame but it's not that Egli, it's another Egli. Steve, to be precise.
No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.