My sponsored 78 shovelhead build thread


#881

Have you re-checked the valves? Maybe intake are a little tight when hot. Can they even be adjusted?


#882

slack-lining saved your life here?


#883

They are hydraulic lifters, so, while they can be adjusted, I don’t know how much difference the adjustment makes. But checking them IS a good idea.

      • Updated - - -

Probably not. I suspect it was one of those things that looked sketchier than it actually was.


#884

If it starts hard when hot check your timing it may be a little advanced. Check lash and follow the adjustment procedure. I’m sure the book you have has the proper method in it.


#885

(expects video shortly)


#886

No offense, engineers always set lash too tight…


#887

I’m glad both of you chimed in.

I’m going to C&P a post I put on chop cult:

The first thing I decided to do was throw a compression gauge on it. I got 60 front and 30 rear. Not so good. I’d kick it about 5 times with the throttle wide open. It’s 7.5:1, so I would expect it to be around 110 max. Being that I’m kicking it, I’d expect it to be 90 psi or so.

I have hydro lifters on the bike, i thought maybe I had a collapsed lifter or something, so I checked each pushrod and found that the rear cylinder intake valve was adjusted incorrectly. I readjusted them all and the bike started first kick 4 times in a row. (It’s late here and raining so I can’t go ride around).

Thinking everything was fixed, I put the compression gauge back on it.

Rear cylinder first kick goes to 60psi. Second kick, 90 psi.

Front cylinder first kick maybe 15-20, second kick 30, subsequent kicks will bring it up to 70 but very slowly.

Next, thinking that I had a bad valve or badly seated rings (or worse) I put a leakdown tester on there. At TDC both cylinders I had less than 5% leakdown. Less really. I was shocked (and glad) to see such low numbers. (I also had checked to see what the leakdown was with the pushrods removed and the motor at BDC and got the same numbers).

So I know:
the valves are sealing perfectly
the rings are sealing perfectly (at least at TDC and BDC)
the pushrods are correctly adjusted

Something just doesn’t seem right. Could it be that the cam is a tooth off? Is there any clever way to easily check this without removing the magneto side cover? (this involves removing my exhaust and brake linkage, which is a task in and of itself).

At this point I’m happy because I can actually start my bike without looking like a dick kicking it 100 times, but wonder if I should do some further investigating into the difference in compression.

Anyone have any insight? I only ran it for a couple seconds each time I started it, so maybe the front lifters didn’t pump back up. Once I can run the bike for a little longer I’ll try do a warm comp test, but I’d still like to hear opinions and thoughts.

I did also reset the static timing using a multimeter. I was a few degrees off previously.

      • Updated - - -

exactly. (but it was too loose)


#888

How far down can you lower the forks in the triple clamps? Moving them slightly down can help a bit with the headshake.


#889

I’m hoping that the tire pressure was the main source of the issue. Moving the forks around changes the trail geometry a bit, but if my math is right I should have a very good trail measurement.


#890

Your cam timing could be off. I know of no good way to check the cam timing other than taking the cam over off.

Adjusting the push rods can be a real PITA. I doubt your lifters collapsed.


#891

I have been thinking about cam timing more, and starting to wonder if it could be that. Wouldn’t the cam timing be off equally between front and rear cylinders? If the cam is one tooth retarded, then wouldn’t that change both cylinders? I’d think it would have an effect on both cylinders equally, not just one.


#892

Yes but where in cycle is the question. One tooth off could be the exhaust opening while the intake is on base lobe on the other cylinder etc. Not actual but example. After looking at your setup today I would check all the mechanical then find out what idle fuel pressure should be from the carb manufacturer.


#893

What carb are you running? s&s?


#894

I swear I didn’t intentionally match my motorcycle.


#895

You should make the pants match so when you’re driving down the road people think all you are is a torso on a bike.


#896

can’t wait to hear a drive by video hitting boost.


#897

https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xpf1/t1.0-9/10418342_10152556792204365_1171922206177522530_n.jpg


#898

I’m assuming some tweaks solved the wobble.

What’d you find out on timing, front comp?

BOOSTZ VIDSZ?


#899

There is no answer that I’ve found for the front cylinder being weird. I checked the cam timing and it’s right. I checked all the pushrods again. I checked the lifters, I did a compression test, single kick with the pushrods out, start at BDC, both go to 90psi one kick. But it runs and I’m just going to investigate it later.

There is still a little wobble at speed but inflating the tire definitely helped greatly. I expect it to wear out pretty quickly, so when it does I’ll just get one that’s a little more road friendly.


#900

Have you consulted Dave?