View Full Version : new member, old shovelhead problem

08-27-2004, 09:46 PM
have an '82 shovelhead which i recently had rebuilt at approx 25,000 miles. the shop bored it .010" new weisco 10:1 pistons new valves, guides and seals. all seemed fine except for one slight problem. ever since the rebuild it fouls plugs. it's been back to the shop 4 times and each time they take it all back apart rehone new rings new valve guide seals and each time it still fouls pluge. they are the correct heat range and i am breaking it in very gently and changing the oil frequently. when i say fouls plugs i mean within 160 miles one of them stops sparking due to an oil whisker. compression test reads about 10% bleed down but there are only 500 miles on the last set of rings. i just came back from the shop and i looked at everything i could think of and all seems fine. there is no evidence of blowby around the rings and the wear on the cross hatch looks even and normal. no cracks in the heads i can see. just lots of carbon and oil. the stem is wet with oil in the ione exhaust valve which i thought was weird but the guy (who has been a shovel "head" for years) says the exhaust valve doesn't run hard enough to burn the oil.

his plan is to rebuild it yet one more time using softer "race" rings this time and then rebuild the heads. i think we are missing something such as a blocker oil return or bad breather valve??? i'm running straight 50 wt and changing the oil every 200 miles during breakin. i run it very gently during breakin, btw

it is not too rich; the plugs are definitely oil fouled

can anyone help?



08-27-2004, 10:09 PM
welcome seedbag....

geez, sounds like you've done your homework here. if it had a blocked return, oil would stay up in the rocker covers and you'd definitely be able to trace it out.

you never said, but is it a stroker motor? if so, sometimes the breather gear timing requires some tweaking to compensate for the faster piston speed and longer event duration.

if not- that 10% leakdown figure does raise an eyebrow. during the leakdown test where do you hear the air? through a valve or through the case?this might also help pinpoint it.

lastly- even though the guy wasn't too excited about the valve guide dripping- that could- especially on a higher compression engine- be a big contributor. higher compression combined with an eggaerated cam profile with a good amount of overlap might tend to draw some oil in during the overlap event. worth a look. i don't consider any oil losses on an engine as "normal"...

let us know...


08-27-2004, 10:25 PM
Hi Again Seedbag

Junior may bo on to something with the valve guides.

I had a Shovel that gave me all sorts of problems very simular to this, problem was the valve guides.

This bike ran great except when it started getting hot then the oil would seep past the guide & would start smokin out the rear cyl, I ended up repalcing the seals a couple times because it was easy but kept coming back then I finally broke down & replaced the guides which solved the problem. This is a known bad area of the shovels of the AMF era.

What plug is fouling ?

08-27-2004, 10:28 PM
again it sounds like you got your shit togeather , the first thing i see is that you are useing 50 weight to break in the moter you should be running a liter oil or a 15/50 oil most were and tear on a motor is in the start up and the first few min of running so that 50 weight is not lubeing those rings or the rest of your moter enought , the next thing is have you cut the valve guide stems for unbrilla seals that would help a lot with the oil on your exsaust valve softer rings will seat better for you and last but not least cheak breather timeing

08-27-2004, 11:07 PM
thanks to all you gentlemen for your ideas.

it is not a stroker. all we did was go 010" over and bumped up to 10:1 comp.

on the leakdown the noise was from cases...it seems like the valves seat fine, still not too sure about the guides. although they are new maybe clearance is too much?? i'm not sure what style seals he uses. i'm guessing the unbrella style seals better when pressurized....i will check.

good point on the multi wieght oil for break-in, i hadn't thought of that.

if the oil in the combustion chamber is getting past the rings is it likely i could see liquid oil on the exhaust valve stem?? i was running it fairly hot before the tear down and i would;ve thought any oil blowing by the exhaust port would cook off the valve stem????

did i mention there was alot of burnt oil all over the top o fthe piston and inside (piston side) of head? the thing that seems so strange to me is there is on;y 10% leakdown. also there is little or no visible smok out fo the exhaust pipes.

btw both cylinders are doing it.

thanks again


08-27-2004, 11:22 PM
from what you are describing it almost sounds like you have a restickted oil return alowing the oil to stay up in the head to long, if the rings were alowing that much oil to get buy you would not be able to go 5 miles before foiling a plug also there would be lots of smoke so that puts us back to the valve area at this point the best i can offer up is a good close inspection of everything dont trust anything as being good tell you have cheaked it out sometimes when you are right on top of it you can miss the ovious so step back and take it slow and easy one time i was doing a evo that kept sucking head gaskets i was on the 3rd set when i finly noticed the studs from the motor were uneven causeing me to torge wroung and i would have bet i cheaked it but that was the problem IT IS THE LITTLE THINGS THAT WILL GET YOU

08-27-2004, 11:28 PM
Just my .02

With the leak down test figures I'm thinking valve guides or upper cyl. oil return (rocker boxes.) Check the cyl. oil return valleys (holes) for trash.
Check valve guides for slop and proper rocker arm to stem angle.

Another thought is cyl. boring. Might want to check for out of round and taper.Cast iron cyl. are usually pretty forgiving but what the hell ck. it.

I like standard cast rings on shovels, maybe the rings are'nt seating well when running but pass leak down test when static. Shit, sounds silly but seen weirder stuff.



08-27-2004, 11:33 PM
along the same lines as rw....

if your machinist did not use torque plates while boring/honing and he was taking big bites- the bore could actually be suspect...


08-28-2004, 07:32 AM
Welcome Seedbag!

With all your rebuilds, the first thing that comes to mind is the oil screen top of the oil pump. I forget offhand where it is in the scheme of the oil path so it may be totally unrelated. But a friend was having all kinds of trouble with his bike - including fouled plugs - and when I pulled it (he didn't know it existed), it was clogged tight. It worked, anyway.

It's just something a lot of folks overlook, and just thought I'd toss it out there. Like Wrecker said, "it's the little things"....

08-28-2004, 08:12 AM
See there seedbag, at least no one is telling you your carb is to fat :lol: Guys, we been over all those things in the other forum with the exception of the torqe plates. That one slipped me. Good one JR. Another thing is he is fouling the plugs at around 150 miles. Seed said everything has been triple checked and checked again. Might it be possible that they are tearing down before the rings have a chance to seat and they are starting a cycle all over again? I ran out of ideas, thats why I directed him here. I still suspect a blockage in the oil return path resulting in flooded rocker boxes. I suppose you could rule that out by running it and popping a pushrod keeper. If it was that, you would know right away.

08-28-2004, 04:39 PM
absolutely, big shovel! there seems to be a deeper body of knowledge here than i see at cc (no offense towards anyone)

i am liking the idea of the blocked return path in the oil circuit. that with maybe the guide seals not quite right could explain it. also could be the rings but it seems to me (just opinion) that the oil leakage is too much for the amount of bleed-down i'm seeing. i'm thinking the 10% is due to it only having about 500 miles since last fresh rings.

hey wait a minute! maybe this is a great way to break a new top end in. at least i know everything is getting plenty of oil!!!!

let me way i appreciate all the thoughts and help and am heading down to the shop today armed with things to test and check for.

oh and thanks for the welcome. here's a quick pic of my old shovel


08-28-2004, 06:46 PM
Nice looking scoot,very nice.


08-28-2004, 06:51 PM
Geez dood, awesome ride !!! Love the springer!!

Ok now I want a springer front end for my shovel ...


08-28-2004, 09:24 PM
thanks guys

btw as soon as i get this problem corrected and clean it top to bottom and make everything perfect it will be for sale....in case anyone knows of anyone looking for a clean scooter.

i have had it for close to 15 years and i love it but i can't afford to keep it once my new one is on the road.


08-29-2004, 12:36 AM
She sure is a beauty Seedbag!!

Let us now when yor going to sell it, might have a buyer for you ;)

08-29-2004, 09:12 AM
Nice ride. If I had to I'd could get by just looking at it for awhile. Hope things clear up soon...

08-29-2004, 02:23 PM
Just wanted to jump in and welcome seedbag to the forums. drunks

09-06-2004, 02:22 PM
Sure would like to know the outcome of this...

Seedbag? Still with us?

09-07-2004, 03:11 PM
sorry i haven't posted a result yet, i didn't want to be premature. good news is that i have 150 miles on the new rebuild and it runs great. bad news is that i spent some time with my mechanic going over the old engine and found nothiung that looked like it explained the condition. i'm convined it was a head problem and i'm leaning towards the guides.

i will report back at 500 or so miles


09-17-2004, 03:25 AM
Seedbag, have run into this many times especially if the shop isn't real swift on pans, shovels, and iron heads. During the original rebuild if the heads were surfaced, there is a good chance they are not seating completely because the counterbore in the head is shallower than the fire ring on the top of the cylinder. When this happens, there will not be enough crush on the head gasket and on the intake stroke, the vacuum in the cylinder will pull oil from the oil drain down hole, in the head and cylinder, past the head gasket, over the fire ring and into the combustion chamber. I have run into this many times over the decades of machining on Harleys. I will not surface a shovel, pan, or ironhead without remachining the counterbore in the head. This is something I check on every shovelhead I remanufacture, or do head machine work on. If it is borderline, sometimes I will machine a few thou off the cylinder fire ring.
If it is leaking past the gasket and over the fire ring, you can usually tell it when you remove the head by looking for tracking on the gasket and the top of the cylinder between the drain down hole and fire ring. I have also seen them not seat because of warpage. Maybe this will help.

09-17-2004, 08:23 AM
interesting- stc, woulda never thought of that. so essentially what you are saying is that the flycut eliminated the head material necessary for proper gasket crush- is that it? very cool....

sounds like you have a wealth of knowledge to offer the group- glad to have you aboard. i enjoy reading your posts...


09-17-2004, 04:04 PM
Yep! Removing head material on a Pan, Shovel, or Iron head reduces the gasket crush. Glad to help in any way I can.

09-22-2004, 11:12 PM
Soretail welcome aboard. Sounds like we got us a machinist to bounce things off of. Very cool.


09-24-2004, 08:45 PM
Hey guys for the posts. I started in on harleys during the EVO. While I was working on a friends sporty another one of his friends came over with his shovel. Plugs are black as can be. He keeps saying the carb is too fat and continues too lean it out, but I see whats going on. Thanks.