V-Twin "Replica" Pan Heads

[Panacea]

The first place I usually look is the last thing I had my hands on, what caused that spring to break, often times, the new problem is related to the old problem. It probably was just a bad spring, and a coincidence that particular valve isn't doing it's job now. Maybe the excessive rocker arm endplay contributed to guide wear, leading to excessive carbon buildup from oil leaking down along the stem. It's a shot in the dark for sure. I'm sure you'll figure it out!

[Mongrel505558]

Did that valve fit the guide and seat well after the spring was replaced?

Yes. I went ahead and replaced all of the springs and everything fit like it was meant to. I didn't mic the guide bores, but the fit felt fine.

[Mongrel505558]

The first place I usually look is the last thing I had my hands on, what caused that spring to break, often times, the new problem is related to the old problem. It probably was just a bad spring, and a coincidence that particular valve isn't doing it's job now. Maybe the excessive rocker arm endplay contributed to guide wear, leading to excessive carbon buildup from oil leaking down along the stem. It's a shot in the dark for sure. I'm sure you'll figure it out!

The last thing I had in my hands were the brand new fully assembled (less rocker arms and blocks) V-Twin heads. When I transferred the old rocker assemblies from my old heads I used new studs and those annoying locknuts, and the rocker shafts and saddle bores were in good condition. No perceptible slop or end play. When I first installed these heads I measured compression and got about 90 psi for each cylinder with a fresh bore and new pistons and rings. Now after about 600 miles on this top end I'm measuring 130 psi in the rear cylinder and 30 psi in the front. Adding oil into the plug hole doesn't raise the measured compression. Leak down test suggests the front exhaust valve. Removed pushrods for the leak down test and re-installed them per Velva-Touch instructions - tighten 9 flats from initial pushrod/lifter contact for front and 6 flats for rear.

[RooDog]

Removed pushrods for the leak down test and re-installed them per Velva-Touch instructions - tighten 9 flats from initial pushrod/lifter contact for front and 6 flats for rear.
[/quote]

Jim....
What's with the unequal preloading for the F&R pushrods? That makes no sense to me. Any help?
....RooDog....

[Mongrel505558]

Removed pushrods for the leak down test and re-installed them per Velva-Touch instructions - tighten 9 flats from initial pushrod/lifter contact for front and 6 flats for rear.

Jim....
What's with the unequal preloading for the F&R pushrods? That makes no sense to me. Any help?
....RooDog....
[/quote]

That's per the Velva-Touch instructions: "Position the rear cylinder lifter block tappets on the heel of the cam using the method in step 8, then adjust the pushrods as described in step 9, EXCEPT, turn the adjusters out one (1) full turn, or six (6) wrench flats. Expand the sleeves and install retainers".

I think it may be because of the difference in running temperatures of the cylinders. To be honest, I always adjusted them 9 flats front and rear for years. This is the first time I actually followed that particular instruction. After riding the bike long enough for it to get good and warmed up I don't hear any noticeable difference in the tappet or pushrod sounds.

[RooDog]

Jim....
Adjusting hydraulic lifters on a Small Block Ford loosed them one at a time, with the engine running, until the valve lash clattered. I would then tighten it down until silence plus 1/2 turn on the adjusting nut. After letting the lifters stabilize I noticed an additional 1/8-1/2 turn would affect the idle speed and vacuum reading. Why, I don't know why, it makes no sense to me as the hydraulics should take care of any lash/preloading.
So, I wonder if this phenomenon holds true with Harleys?
....RD....

[Mongrel505558]

Jim....
Adjusting hydraulic lifters on a Small Block Ford loosed them one at a time, with the engine running, until the valve lash clattered. I would then tighten it down until silence plus 1/2 turn on the adjusting nut. After letting the lifters stabilize I noticed an additional 1/8-1/2 turn would affect the idle speed and vacuum reading. Why, I don't know why, it makes no sense to me as the hydraulics should take care of any lash/preloading.
So, I wonder if this phenomenon holds true with Harleys?
....RD....

It doesn't make a lot of sense to me that three flats looser or tighter would have an effect on performance, but theoretically I guess it does, since you are changing the valve spring pressure vs. lifter hydraulic pressure relationship. And I can tell you this: Saturday morning after reinstalling the pushrods and setting 6 flats instead of 9 for the rear I sprained my ankle kicking the damn bike. Been limping until today. Compression was almost impossible to kick through. It was never easy before, but this was a surprise. And there isn't any interference or contact going on with pushrods, etc.

Jim

[RooDog]

Jim....
Adjusting hydraulic lifters on a Small Block Ford loosed them one at a time, with the engine running, until the valve lash clattered. I would then tighten it down until silence plus 1/2 turn on the adjusting nut. After letting the lifters stabilize I noticed an additional 1/8-1/2 turn would affect the idle speed and vacuum reading. Why, I don't know why, it makes no sense to me as the hydraulics should take care of any lash/preloading.
So, I wonder if this phenomenon holds true with Harleys?
....RD....

It doesn't make a lot of sense to me that three flats looser or tighter would have an effect on performance, but theoretically I guess it does, since you are changing the valve spring pressure vs. lifter hydraulic pressure relationship. And I can tell you this: Saturday morning after reinstalling the pushrods and setting 6 flats instead of 9 for the rear I sprained my ankle kicking the damn bike. Been limping until today. Compression was almost impossible to kick through. It was never easy before, but this was a surprise. And there isn't any interference or contact going on with pushrods, etc.

Jim

Another great unsolved mystery.....
If the valves are fully seated, regardless of hydraulic, or solids, the compression should be the same. But, if the hydros had bled down over night, lessening the cam's duration, it is conceivable, the the compression would be higher because of the intake's earlier closing. Have you run a compression test on cold vs hot engine?
....RD....

[Panacea]

The intake would also open later in that scenario. The increase from 90 to 130 psi in the rear cylinder could just be because the rings have worn in for a better seal,

[Mongrel505558]

Another great unsolved mystery.....
If the valves are fully seated, regardless of hydraulic, or solids, the compression should be the same. But, if the hydros had bled down over night, lessening the cam's duration, it is conceivable, the the compression would be higher because of the intake's earlier closing. Have you run a compression test on cold vs hot engine?
....RD....

No cold vs. hot compression test yet. I can tell kicking it through hot that the front cylinder is still weak, and I plan to pull the head anyway to investigate everything. I'm hoping the problem is in the head rather than the compression rings since I just had the jugs honed to the new pistons. I'll de-carbonize everything and pull the valves and lap at least the exhaust until I get a leak proof seal when I pour kerosene into the port. Hopefully it's no more than that. Guides are brand new and hopefully good, although I'll check them, too. Motor doesn't burn oil and no trace of oil on the plugs. I know rockers are good. I'll install a new stem seal and hopefully be good to go from there.

Re-reading this post I notice I say "hopefully" a lot. I guess that's a lot of uncertainty, but hopefully I'm right.

[drinner-okc]

Well, I took the plunge this week. Bought a set of 10-1074 V-Twin Outside Oiler Heads with Shovel Ports. After following this thread first thing I'll do is order a set of not V-Twin springs, and better seals.
The box arrived where I work yesterday. I've looked them over, they look good quality.
I'll start another thread with my plan.

[awander]

Well, I took the plunge this week. Bought a set of 10-1074 V-Twin Outside Oiler Heads with Shovel Ports. After following this thread first thing I'll do is order a set of not V-Twin springs, and better seals.
The box arrived where I work yesterday. I've looked them over, they look good quality.
I'll start another thread with my plan.

Looking forward to hearing about your experience!

Hit me up if you need any info!

[awander]

It's been about a year since I got these new heads running on my '52, and I am really happy that I have finally found the new starting routine!

Before I replaced the heads, I took pride in having the bike start on the first kick after ignition was turned on.

Since the new heads, sometimes it would start in 1 or 2 kicks, other times I'd need to kick it 10 or 20 times.

Old routine was:
-ignition off, choke on full, 3 kicks with throttle wide open
-choke on one click, retard timing, ignition on, throttle wide open
-one kick would almost always do it

Since it's been cold and rainy here, I decided to just experiment with the starting routine-multiple times per day-and I think I finally found it!

Same as above, only open the throttle only a little bit on the starting kick.

[Excalibur]

Happy to hear it's all working nicely.

It's very satisfying when you make a breakthrough on starting. I read with interest your experiment routine because a few years back I did much the same. I could get the bike to start and restart in the shed all day. I was feeling very smug, then we went on a pub run. Well the bike wouldn't start but eventually it ran. It was then I realized the whole dynamic was quite different to the shed. Lots of heatsoak, full sun, etc. Soon worked it out...

[Mongrel505558]

Glad to hear it's running well. My V-Twin heads are hanging in there. I replaced the valve gear and swapped my Andrews "J" cam for an S&S "H" Victory cam reproduction. After immediately finding a broken valve spring I didn't trust the valve gear that V-Twin supplied the head with. I still have a pair of STD heads that I can run for more performance. Bike does start easy and runs dependably.