V-Twin Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
My oldie but goodie Fatboy is weeping from the cylinder base gaskets which I understand is a common problem for aging early Evos. I can generally do anything mechanical, but was wondering if anyone has taken on this job themselves. If you have, what problems am I likely to run into?

I installed my own cam and replacement pushrods as well as upgraded the carb to an S&S and also installed a Crane Hyfire ignition previously so I'm not afraid to tackle this, but it's always better to be armed with a little information than not.
 

·
Premium Member
Joined
·
4,733 Posts
It's pretty straightforward. If you did your cams you can handle that job.
You may have to remove the front motor mount to lower the engine enough to remove the cylinders, I'm not sure on the Fatboy.
Check your ring gap and piston groove wear while you've got it down that far.
 

·
Registered
Joined
·
1,424 Posts
It's a straight forward job ... no real tricks. As suggested earlier, check out the bore and pistons along with the rings and if all looks good, stick the gaskets in and you're back on the road. I would ( as many other, past and present EVO owners would agree ) strongly suggest letting your scooter warm up for a minute before you take off each time you fire it up. They ( EVO's ) were/are very temperature sensitive when it comes to base gasket longevity .... just my.02 cents worth .... Been there, done that .... Good Luck!
 

·
Registered
Joined
·
69 Posts
If you're going to pull the cylinders have a hone run through them and replace the rings, and have the valves ground while the heads are off, so basically do a top end.
 

·
Premium Member
Joined
·
3,435 Posts
Did that job once already. Good idea to check the flatness of the cylinder base. Alot of times they weep from the base getting warped. Seems to hold good by the studs but sometimes inbetween warps a bit. I used cometic gaskets that were supposed to eliminate that problem but my rear cyclinder is going to have to come off again.I noticed that the top motor mount was loose and I had a bit of excess vibration. Don't know if that contributed to the failure or not but I'm sure it didn't help.. Regardless, I always let the bike warm up before heading out..Leak or not.
 

·
Registered
Joined
·
345 Posts
The rear cylinder on a fat boy is a real pain. A big dose of patience helps.
 

·
Registered
Joined
·
15 Posts
I would recommend checking out your Block studs.. I mention this because the OEM studs have a 'collar' or a stop just under the threads towards the top of the studs. If your studs have stretched any at all due to age or compression etc.. the head gasket will fail until you change out the studs. Harley put out a service bulliten mentioning changing the studs out to the newer design which did not have a 'collar' up top, but towards the block so that when u torque the heads down, the head bolts are not stopped by the 'collar' and therefore you can prevent any head gasket issues like I had on my EVO. Just my .02 as the previous guy mentioned..
 

·
Registered
Joined
·
15 Posts
Did that job once already. Good idea to check the flatness of the cylinder base. Alot of times they weep from the base getting warped. Seems to hold good by the studs but sometimes inbetween warps a bit. I used cometic gaskets that were supposed to eliminate that problem but my rear cyclinder is going to have to come off again.I noticed that the top motor mount was loose and I had a bit of excess vibration. Don't know if that contributed to the failure or not but I'm sure it didn't help.. Regardless, I always let the bike warm up before heading out..Leak or not.

Yes going through the run cycles will help, I was instructed to do this many times.. short ride.. cool down, short ride... cool down..etc.. and not to abuse it while doing these run cycles just up to temp, and shut er' down and let cool. great for bar hopping in my opinion.
 
1 - 9 of 9 Posts
Top