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#412665 - 01/10/12 11:58 am Clunk...WTF...  
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BSA-Jay Offline
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Boonton, NJ, USA
So..I have finally removed the trans from my 70' A66, and im ready to install the new one... but before i did i wanted to make sure the upper end of the motor was in proper working order. I re-assembled the spindles, tappets etc etc.. torqued everything down all proper like,installed the push rods and set the valve gap.
Up until this point the Motor cranked smooth by hand, even had decent compression.(well as close as i can tell cranking the motor by hand and covering the plug port),... But now that i have installed the components to the head it only cranks about 1-1.5 turns and stops dead with a light "clunk" in either direction. I have never encountered this before on any motor I've had... Anyone have any idea as to what is causing this??


1967 BSA Lightning(w)
1969 BSA Thunderbolt(e)
1966 BSA Thunderbolt(?)
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#412667 - 01/10/12 12:09 pm Re: Clunk...WTF... [Re: BSA-Jay]  
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Mattsta Offline
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Surrey UK
I think you need to check your valve timing

It sounds like you might have valves open at TDC


1952 Triumph T100 in a BSA A7 Frame
#412684 - 01/10/12 2:18 pm Re: Clunk...WTF... [Re: BSA-Jay]  
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leon bee Offline
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arkansas
Do those pushrods again.

#412687 - 01/10/12 2:23 pm Re: Clunk...WTF... [Re: BSA-Jay]  
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wak Offline
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derby england
sounds like a pushrods not fitted properly at the bottom or on the wrong follower


BSA CYCLONE
BSA METISSE
TRIUMPH TR6C
BSA BUSHMAN
INDIAN WOODSMAN
#412699 - 01/10/12 2:51 pm Re: Clunk...WTF... [Re: wak]  
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BSA-Jay Offline
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Boonton, NJ, USA
I have the intakes on the outer followers and the exhaust on the inner 2. I did have a bit of trouble with the right side exhaust rod.. it was hanging up a bit but got it seated properly.I then removed the pushrods and checked the piston position before installing again.. it looked correct. I had assumed that since the motor was redone recently that everything "should be set correctly".. as i didn't make any changes, only removed the tranny.


1967 BSA Lightning(w)
1969 BSA Thunderbolt(e)
1966 BSA Thunderbolt(?)
#412779 - 01/10/12 8:56 pm Re: Clunk...WTF... [Re: ]  
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Lannis Online content
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Central Virginia
Originally Posted By: 1968BSA
Sounds like that to me too

Whip the rocker cover off and take a plug and and drop a rod down to see how high the piston is, then try and put it in gear and turn the wheel backwards

Hopefully you haven't done any damage.

Do your valve timing maks line up?


Unless he took the inner timing cover off, and the idler gear came out with it, the timing marks had no way to change ....

Gotta be pushrods on the wrong cam lobes ...

Lannis


OK, I admit it, I'm addicted to brake fluid.

But I can stop any time I want.
#412893 - 01/11/12 11:58 am Re: Clunk...WTF... [Re: Lannis]  
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BSA_WM20 Online content
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Sydney Australia
Also have a close look at the valve ends.
You can get a little rust on the stem when the head has been sitting for a while.
This is oft just enough to make the valve jamb open and smack the piston.


Bike Beesa
Trevor
#412906 - 01/11/12 1:34 pm Re: Clunk...WTF... [Re: BSA-Jay]  
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A.k.a Homer Offline
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Ponoka ,Alberta,Canada
Do you have the right head on it ?


Aka homer


A day with out learning something new is a bad day indeed.
#412955 - 01/11/12 6:04 pm Re: Clunk...WTF... [Re: A.k.a Homer]  
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BSA-Jay Offline
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Boonton, NJ, USA
BSA,
The valves are seated correctly, i have a tendency to oil all metal bits on the head and wrap them it a plastic bag while off the motor.

Homer,
yes, its the head that came with the motor as well as the pistons, cam etc etc..., for a Stock A65 Thunderbolt.

I'm going to take another crack at it Tomorrow(thurs)I'll look into all sugestions.

Thanks alot guys, I'll let you know how it goes.

Last edited by BSA-Jay; 01/11/12 9:16 pm. Reason: cause i made an oops....

1967 BSA Lightning(w)
1969 BSA Thunderbolt(e)
1966 BSA Thunderbolt(?)
#413058 - 01/12/12 10:38 am Re: Clunk...WTF... [Re: BSA-Jay]  
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wak Offline
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derby england
Did you disturb the cam idler pinion when you took the timing cover off to change the tranny?


BSA CYCLONE
BSA METISSE
TRIUMPH TR6C
BSA BUSHMAN
INDIAN WOODSMAN
#413096 - 01/12/12 6:08 pm Re: Clunk...WTF... [Re: ]  
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BSA-Jay Offline
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Boonton, NJ, USA
Originally Posted By: 1968BSA
I think there might be a bit of miss understanding, I was reffering to the pushrods sitting on the ball ends of the tappets and rockers, it's all to easy for them not to seat here, regardless of if the valves are ok or not

Sorry 1968, i was replying to BSA 420's reply concerning the Valves seating/ rusting...


1967 BSA Lightning(w)
1969 BSA Thunderbolt(e)
1966 BSA Thunderbolt(?)
#413098 - 01/12/12 6:24 pm Re: Clunk...WTF... [Re: wak]  
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BSA-Jay Offline
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WAK,
I may have... I'll look tonight when i get over there.
If i did all i should have to do is set the pistons @ 28 degrees before TDC, then re-install correct?? Its been like 8 years since I've had to do anything with the bottom end of the motor so im a bit rusty.

J


1967 BSA Lightning(w)
1969 BSA Thunderbolt(e)
1966 BSA Thunderbolt(?)
#413103 - 01/12/12 7:04 pm Re: Clunk...WTF... [Re: BSA-Jay]  
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Alex Offline
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Seattle
Originally Posted By: BSA-Jay
WAK,
I may have... I'll look tonight when i get over there.
If i did all i should have to do is set the pistons @ 28 degrees before TDC, then re-install correct?? Its been like 8 years since I've had to do anything with the bottom end of the motor so im a bit rusty.

J


28 whu? All you have to do is line up the timing marks.


A smattering:
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sixtyseventy Lightboltrocket road racer...and many more.
#413147 - 01/12/12 11:36 pm Re: Clunk...WTF... [Re: BSA-Jay]  
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Jon W. Whitley Online content
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Vermont
J,

I could be wrong but it sounds to me like you do not have a workshop manual. You will need to remove the idler pinion to re-align the timing marks and make certain the valve timing is correct.



Originally Posted By: BSA-Jay

If i did all i should have to do is set the pistons @ 28 degrees before TDC, then re-install correct?? Its been like 8 years since I've had to do anything with the bottom end of the motor so im a bit rusty.

J


Jon W.


1957 6T Thunderbird 650
1971 TR6R Tiger 650
1955 Tiger 100 - Project
1970 BSA A65F 650 - Project

#413185 - 01/13/12 7:10 am Re: Clunk...WTF... [Re: BSA-Jay]  
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DavidP Offline
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Gnashville
It also helps to back off the valve adjusters so nothing is under tension when you rotate the cam shaft to align the gears.

That said, I had a similar problem years ago with a triple. I got resistance to turning in each direction. Turned out that at least one tappet was tight in its block. You didn't swap tappets around, did you?


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
#413196 - 01/13/12 12:40 pm Re: Clunk...WTF... [Re: DavidP]  
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BSA-Jay Offline
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Boonton, NJ, USA
No,i do not have a proper workshop manual only the cheeseball Hanes manual that covers like 4different BSA's, and what i can remember from my other rebuilds...
DavidP, this motor had nothing in the upper end when i got it, i ordered all new spindles, rockers, tappets and rods, and when i assembled i left them all less than hand tight.

I did however check the Pinion gear and it was in line.. .checked the Push rod seating which also looked ok... until i sent a dental mirror down the tower to the cam followers and cranked the motor did i realize the problem... somehow the left exhaust follower wasn't seated straight.. it was cocked to the left(almost like someone jammed a flathead down there) causing the rod to jam into his neighbor.

2 hours, and a new set of cam followers later problem solved... Although i did notice a crack in the tower so a new set of Cylinders are in order

thanks Everyone for the advice, I appreciate it.


1967 BSA Lightning(w)
1969 BSA Thunderbolt(e)
1966 BSA Thunderbolt(?)

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