Jockey Journal Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
I recently acquired a 61 fl motor,the top end is off as well as the front cylinder my question is how can you tell if it has stroker or not without splitting the cases. First engine build and would appreciate the help.
 

·
Banned
Joined
·
2,014 Posts
Roll the engine over until the rear piston is all the way to the top. Lay a straightedge across the top of the cylinder and measure wher it is. Run it all the way down and do the same. That number( difference between the two) is the total stroke. A stock '74 is 3-31/32nds. If your number is higher it is stroked.
Robbie
 

·
Registered
Joined
·
2,485 Posts
I recently acquired a 61 fl motor,the top end is off as well as the front cylinder my question is how can you tell if it has stroker or not without splitting the cases. First engine build and would appreciate the help.
Not being a SA here, but sounds like you need a service manual. It will answer all the factual dimensions you need to measure, build and repair the motor. Although I am sure someone will chime in. But even then, you should have one, for future reference. Parts manual helps too.
 

·
Banned
Joined
·
2,014 Posts
Since he was asking about a 1961 FL I only gave him a number for 74 CI as 61 CI engines ended in '52 and the crank wont fit the later cases. 61 CI engines also have a smaller bore, 3-5/16 as opposed to the 3-7/16 of a 74 CI.
If someone truly wanted to though they could build a 61 CI engine out of any pan with a little machine work and small bore cylinders. Then you would be making a dog into a lazy dog!
Robbie
 

·
Registered
Joined
·
139 Posts
Since he was asking about a 1961 FL I only gave him a number for 74 CI as 61 CI engines ended in '52 and the crank wont fit the later cases. 61 CI engines also have a smaller bore, 3-5/16 as opposed to the 3-7/16 of a 74 CI.
If someone truly wanted to though they could build a 61 CI engine out of any pan with a little machine work and small bore cylinders. Then you would be making a dog into a lazy dog!
Robbie
I must have been asleep when I read that. My brain saw 61, so I thought he was asking about an el.
 

·
Registered
Joined
·
972 Posts
I was wondering about that....1961 or 61" , if 61' then 3.5" stroke ,glad someone else jumped in.

rubone; wouldnt it be higher rev?
I always wondered about 74" bore and 61" stroke = 64.96cui by my calc close to square.
XR750 and s+s 4 x 4 are square. (not saying pan is up there)
I think Trock was doing that , not sure....
 

·
Banned
Joined
·
2,014 Posts
I have built several 68CI engines using 61 flywheels and 74 barrels at 3.5 inch bore. They rev nicely and pull hard as well as being very smooth running. I like them well enough that I plan to build one as my next knuckle project, a '40s TT replica.
H-D themselves used such an engine in the '40s for some of their military projects.
Robbie
 

·
Registered
Joined
·
972 Posts
That sounds pretty damn good to me , Id expect it to be common in that case , go for revs instead of stroke.
Im guessing the 74 case has larger cavity for the cylinder base and the top of the barrel needs skimming to match the 61 stroke.

like the sound of that knuckle
 

·
Registered
Joined
·
214 Posts
I have built several 68CI engines using 61 flywheels and 74 barrels at 3.5 inch bore. They rev nicely and pull hard as well as being very smooth running. I like them well enough that I plan to build one as my next knuckle project, a '40s TT replica.
H-D themselves used such an engine in the '40s for some of their military projects.
Robbie
Did you have to use a 61 cam?
 
1 - 12 of 12 Posts
Top