BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
JWood Auctions JRC Engineering dealers JWood Auctions
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
Blapper
Blapper
Kent UK
Posts: 4,542
Joined: August 2007
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
17 registered members (Carl), 191 guests, and 406 spiders.
Key: Admin, Global Mod, Mod
Newest Members
Dan1818, Konaflyer, Begbie, Andrew Fallo, Zack Banks
10419 Registered Users
Top Posters(30 Days)
btour 85
Rohan 77
Triless 70
reverb 68
Popular Topics(Views)
713,588 mail-order LSR
Forum Statistics
Forums34
Topics68,326
Posts665,175
Members10,419
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate Thread
Making a Piston Stop out of a Spark Plug #206409
07/13/07 2:10 pm
07/13/07 2:10 pm
Joined: Jul 2002
Posts: 604
England
Tom_dup1 Offline OP
BritBike Forum member
Tom_dup1  Offline OP
BritBike Forum member

Joined: Jul 2002
Posts: 604
England
I've seen references to making a piston stop out of an old spark plug. Have done a search but can't find anything. I want to make one so that I can accurately measure TDC (with a degree wheel) without taking the head off to use a dial gauge. I want to dial the cam in on my B40 scrambler.

Anyone got the recipe?

Thanks

Tom

Support Your #1 BritBike Forum!

Check out British motorcycles for sale:
British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Check out British motorcycles for sale:
British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Re: Making a Piston Stop out of a Spark Plug #206410
07/13/07 2:38 pm
07/13/07 2:38 pm
Joined: Apr 2002
Posts: 716
Out There!
N
Nick Offline
BritBike Forum member
Nick  Offline
BritBike Forum member
N

Joined: Apr 2002
Posts: 716
Out There!
knock the guts out of a spark plug - braze/weld a nut on the top - screw a bolt down the center - use another nut to lock the bolt in place - if your're timing a high performance engine and a valve hits the plug stop, remove stop, turn engine until valve returns to seat and re-install stop to catch piston on its way back up.


When people who should have known better cautioned me about the dangers of motorcycle racing, I always told them that a fear of death is nothing more than a fear of life in disguise.
Re: Making a Piston Stop out of a Spark Plug #206411
07/13/07 2:45 pm
07/13/07 2:45 pm
Joined: Jul 2002
Posts: 604
England
Tom_dup1 Offline OP
BritBike Forum member
Tom_dup1  Offline OP
BritBike Forum member

Joined: Jul 2002
Posts: 604
England
Excellent, thanks Nick!

Re: Making a Piston Stop out of a Spark Plug #206412
07/13/07 3:15 pm
07/13/07 3:15 pm
Joined: Feb 2004
Posts: 1,956
Flint,Mich
norbsa48503 Offline
BritBike Forum member
norbsa48503  Offline
BritBike Forum member

Joined: Feb 2004
Posts: 1,956
Flint,Mich
If your going to the trouble try to make sure that the stop is long enough to stop the piston at about 30 degrees. As Mr. Panic has stated it's better than one that stops it at just 10 degrees. Put a bull nose radius on the end of the bolt at the contact spot. On a Norton this is about an inch and a 1/4 long and a diameter of .160 will just miss the valves.


norbsa
1960 TR6
1963 Super Rocket
1965 650 Star
1966 441
1968 Thunderbolt
1969 Twinkle 250
1972 Fastback
1974 Roadster
1970 S.S
Way too many BSA's not named
http://decentcycles.com
Re: Making a Piston Stop out of a Spark Plug #206413
07/13/07 5:21 pm
07/13/07 5:21 pm
Joined: May 2005
Posts: 112
Hammond, LA
L
liaison Offline
BritBike Forum member
liaison  Offline
BritBike Forum member
L

Joined: May 2005
Posts: 112
Hammond, LA
About 40 years ago when I thought that a big hammer was a necessary tool for working on bikes, I made a piston stop by finding an old bolt that was a semi-interference fit in the spark plug body and pounding it home. The piston stop is still in my tool box, but the hammer has been retired.

Brgds,

Jim

1966 Triumph T120R
2005 Suzuki DL650 V-Strom


Brgds,

Jim

1966 Triumph T120R
2005 Suzuki DL650 V-Strom
Re: Making a Piston Stop out of a Spark Plug #206414
07/13/07 5:29 pm
07/13/07 5:29 pm
Joined: Dec 2004
Posts: 9,553
Scotland
kommando Offline
BritBike Forum member
kommando  Offline
BritBike Forum member

Joined: Dec 2004
Posts: 9,553
Scotland
I used a wooden dowel epoxyied into the plug body, less chance of hurting piston or valve but you have to be very careful not to snap the wood and have to take the head off. Touch wood never had to but there is always a first time .

Re: Making a Piston Stop out of a Spark Plug #206415
07/13/07 10:30 pm
07/13/07 10:30 pm
Joined: Aug 2001
Posts: 1,893
Elko, Nevada USA
dave - NV Offline

BritBike Forum member
dave - NV  Offline

BritBike Forum member

Joined: Aug 2001
Posts: 1,893
Elko, Nevada USA
If you make a 'bump stop', by threading the body of a spark plug for a largish bolt, insure you have a vent hole to allow compression pressure to escape. And as has been mentioned, be sure to round off the end of the bolt to prevent marring the top of the piston.


Dave - NV
Re: Making a Piston Stop out of a Spark Plug #206416
07/13/07 11:23 pm
07/13/07 11:23 pm

A
Anonymous
Unregistered
Anonymous
Unregistered
A



"insure you have a vent hole to allow compression pressure to escape"

This is an excellent and frequently overlooked point. If any compression is trapped near TDC it will tend to rock the crankshaft back away from TDC, and may be small enough not to be easily detected - but will make the measured distance useless.
If possible, the hole should be large to vent the cylinder without delay. If the hole needs be small, it's important that you wait until the escaping air stops before proceeding.
Some of the softer plastics can be threaded 14mm, drilled, and won't damage the piston on contact but I don't know which; shop-made tool seen long ago.

Re: Making a Piston Stop out of a Spark Plug #206417
07/14/07 1:29 am
07/14/07 1:29 am
Joined: Nov 2004
Posts: 1,694
georgia
T
trumpetloon Offline
BritBike Forum member
trumpetloon  Offline
BritBike Forum member
T

Joined: Nov 2004
Posts: 1,694
georgia
If you use a smooth rod equipped with a set screw locked collar, you will be able to take dial indicator measurements directly from the rod through the center. Think timing locator tool writ large; with a repeatable stop for precise measurement. HTH!!! beerchug


1974 TR5T
Re: Making a Piston Stop out of a Spark Plug #206418
07/14/07 3:23 am
07/14/07 3:23 am

A
Anonymous
Unregistered
Anonymous
Unregistered
A



but... you need to do the trig re: the plug angle to determine the actual movement - the dial motion will always be larger. What's the plug angle? IKBA.

Re: Making a Piston Stop out of a Spark Plug #206419
07/15/07 8:17 pm
07/15/07 8:17 pm
Joined: Nov 2004
Posts: 1,694
georgia
T
trumpetloon Offline
BritBike Forum member
trumpetloon  Offline
BritBike Forum member
T

Joined: Nov 2004
Posts: 1,694
georgia
Panic; please 'splain...triangles confuse me. Isn't the motion in a straight line regardless of angle of inclination and hence "one to one"?


1974 TR5T
Re: Making a Piston Stop out of a Spark Plug #206420
07/16/07 6:17 am
07/16/07 6:17 am
Joined: Jul 2002
Posts: 604
England
Tom_dup1 Offline OP
BritBike Forum member
Tom_dup1  Offline OP
BritBike Forum member

Joined: Jul 2002
Posts: 604
England
Thanks. The tool is now made! I included a vent hole and the welder accidently made another. Damn thin those spark plug casings.

Re: Making a Piston Stop out of a Spark Plug #206421
07/16/07 2:49 pm
07/16/07 2:49 pm

A
Anonymous
Unregistered
Anonymous
Unregistered
A



Look at it this way: if the plug thread were horizontal, an indicator in the plug hole wouldn't move no matter what the piston did - its movement could be infinite and would still show nothing. If the plug thread were vertical (parallel to the bore axis) the indicator movement would be exactly the same as piston movement.
In between (which is almost everything except some flatheads) the indicator distance is always larger since it's a vector: one component is horizontal (based on the angle) and the other is vertical (based on piston movement).
To find the actual piston movement, multiply the indicator reading by the cosine of the plug angle.
If 0 is a vertical plug, a 30 plug indicator reading will be higher than the actual movement; multiplied by the cosine of 30 (.866), each .100" of indicator travel = .0866" of piston movement.
45 plug: .7071, 15 plug: .0966.

Re: Making a Piston Stop out of a Spark Plug #206422
07/16/07 3:33 pm
07/16/07 3:33 pm
Joined: Nov 2004
Posts: 1,694
georgia
T
trumpetloon Offline
BritBike Forum member
trumpetloon  Offline
BritBike Forum member
T

Joined: Nov 2004
Posts: 1,694
georgia
Thanks for the lesson for the mathematically challenged (me)!!!!


1974 TR5T
Re: Making a Piston Stop out of a Spark Plug #206423
07/16/07 3:46 pm
07/16/07 3:46 pm

A
Anonymous
Unregistered
Anonymous
Unregistered
A



Now if we had good data on spark plug angles for some common engines, I could do up a chart for the board of indicator motion per .001" by brand and model...


Moderated by  Allan Gill 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.6.2