Hi All,

My name is Ron, from the Netherlands. Long time biker, wrencher and finally a proud owner of a '96 Dyna. Bought it last year, matching numbers, with about 35K miles on it. Love it, but it comes with a price...

I did a compression test before, measuring 150 psi on the front and 145 psi at the rear, cold. I did the test because once in a while it blew the oil cover from the tranny which caused me to be suspicious about blow by gasses. I've also heard something like piston slap going WOT in lower rev ranges sometimes, but the test proved otherwise. In warming up phase, I could hear a tick as well, which I considered to be the valve train. It would decimate when fully warmed up, but it was still there. I've no idea whether the cam shaft bearing has been done in the past and have not opened up the right cone yet.

It ran fine for about 1000 miles, until the end of the summer I returned home on one cylinder. Parked it for the winter, checked the carb twice because I thought it was running rich after tuning it because it was running lean. This weekend I checked it for the third time, and again it was running on 1 and a half leg. In the end, I checked the compression again. 150 psi on the front, 60 psi at the rear cylinder. Ok...

I've been wrenching for 30 years on trucks, car, motorcycles and what not, overhauled many types of engines but need some help getting started on this one... I removed the rear valve covers, but for the life of me, I can't feel any valve play. Should I feel play in the first place? Or are the hydraulic lifters pushing out all the play? Or should I only be able to turn the push rods (which I can)? I still seem to have the original push rods. They seem to be none adjustable, intake is marked with blue rings, exhaust with orange ones.

I'm planning to pull the rear cylinder anyway, but don't want to rush things.

How about a leak test? I have not found a way yet to block the engine at TDC (rear cylinder). Is it easier to remove the rocker boxes and to do a test at BDC? Or can I remove the lifters somehow? Or is their a way to block the engine? I've read about blocking the rear wheel in high gear, but think the play in the drive line will allow the piston to move a stroke opening the exhaust valve again.

Any thoughts? Tricks? Tips?

Thanks in advance!

 

Welcome to the forum, Ron!

My only thought on this is going from 145 to 60 in 1000 miles isn't just ordinary wear. Something broke. You said you don't want to rush things, but I think it's time to pull the top end and see what's what.

 

^^just what he said^^

Welcome to HD forum.

 

Thx people,

Yeah, sometimes you need someone else to say that to get that point across...

Anyway, by the looks of it, I can pull the top end without removing the engine from the frame, amirite?

The 1000 CC Rotax (1st gen Aprillia twin) engines I used to work on, allowed you to work on the rear cylinder and keep the front as is. Is a Harley as forgiven, or should I pull the front cylinder as well? If yes, can also the front be done with the engine in place?

Cheers!

 

I would do a leak down test before you tear it down so you will know if it is valves or rings before you start...it is not hard to hold it at TDC with bike in gear.

 

This should be done before tear down... Might not have to go too far in... With 35k on it I doubt the rings... I would look at the cam chest as well... Bearing failure can cause different compression readings from front to rear...

 

I'd just rip it apart, rear cylinder only. You know there's a problem, I don't see a reason running any more tests.

BTW you should be able to spin the pushrods. No play though, just spin. Them valve springs take a LOT of power to compress.

 

I will, found out the cylinder base gasket is also leaking, I have to be there anyway. So thx, also for the additional info
Hope to have some pictures soon...

Thanks for that, I'll have a look at the bearing as well.

 

The "may as well's" and "as long as I'm at it's" kick in!

(New cam, new pistons, cleaned up heads.......)

 

Lol, yeah, prolly

Tomorrow i'll know more.

Again, thanks all for the warm welcome. Things already seem less bad than they did this morning. There is nothing some good advice (and a bottle of Johnny Walker) can't fix

*edit*

Lmao, just now it dawns to me I joined this board in 2008!? It took me 9 years to buy a Harley, I promise it'll take me less than that to get it back on the road