i picked up a custom bobber this summer that had a Harley evo BT engine in it. I know very little about the condition of the engine, up until this point it ran perfect. Cruising along one day started getting a mechanical failure, brought it home and found the lifter failed. Broke the guide block and ruined the cam.

So time to replace it all, I got the EV27 cam with some s&s lifters and adjustable pushrods. Cleaned everything and reinstalled it all.


I have the timing marks marks lined up correctly
with the pinion, breather and cam. However at this point of those components being lined up the motor is not at TDC anymore (I read that tdc doesn't matter?? True or false)

Well I finally have gotten it all back together, started the bike and only the rear cylinder is firing..? I messed with the timing plate trying to get it set but that front cylinder just isn't firing. I've checked for spark and it's there, fuel is good. Followed up with a compression test and was getting 100-120 on cylinders so we are okay there.

Is something not timed right when I had to replace the cam? Does the motor just have to be at TDC and the timing marks on the cam and breather lined up? Any advice, I'm so ready to get back on the road!

the picture shown is of the engine at TDC and the timing marks not lining up. When I originally installed it all the marks were all lined up (but not at TDC) am I having a brain fart, what's going on

 

When installing the cam the and lining up all the marks in the cam chest the piston "WILL NOT BE ON TDC".......

The only time you need TDC mark on the crank is when your setting your base timing... Do you have adjustable pushrods? And what ignition are you using?

 

Yea I've gotten a set of adjustable pushrods and still using the stock Harley ignition system.

 

Do you have single fire or dual fire coils??
If dual fire switch the wires and see if the dead cylinder moves to the other side.

While you don't need the motor at TDC when installing cam you do need it at TDC when installing the bottom rockerboxes unless you are using adjustable pushrods.

 

https://rideapart.com/articles/brief-history-harley-davidsons-big-twins

you've seen it in print a thousand times

 

BT- Big Twin

The service manual in using states "if compression is 90 psi or above, and not more than 10% difference between cylinders, compression is considered normal".

i am using adjustable push rods, I'll have to try switching the wire to see if it follows

 

What did you have 12.5 to 1 compression?

8>1 = 102.9 psi
8.5>1= 102.9 - 110.25 psi
9>1= 110.25 - 117.6 psi
9.5>1= 117.6 - 124.95 psi
10>1= 124.95 - 132.65 psi
10.5>1= 132.3 - 139.65 psi
11>1= 139.65 - 147 psi
11.5>1= 147 - 154.35 psi
12>1= 154.35 - 161.7 psi

I have never seen 165 on any motor I have checked the compression on...this chart is supposed to be close...my stock evo does about 110.

 

I was wondering what a "BT" engine is also.

Ditto on the TDC not mattering on the cam gear install. Cam gear to pinion gear, then breather to cam gear and you're set.

 

THANK YOU! I always read these huge numbers, but every stock Evo I've tested comes in at around 110/120 more or less.

Then everyone tells me "REBUILD THAT THING! COMP IS TOO LOW!!!"

And I'm all like WTF you talking about?!?

 

All I can tell you is what the guage read.
I had stock pistons with the EV-27 cam.

FWIW the bad boyz calculator isn't even close to that chart.
It told me that 10-1 pistons should be getting around 180.