Annoying barrel leak

Anything I'm missing??

OK, short history, got the head & barrels/pistons worked on by Jim Comstock, so lets say the work has been done by somebody who knows what they are doing!!

After the rebuild I had an annoying leak from the front of the engine, it 'seems' to be dribbling down the passageways at the bottom front of the barrel. I used a new flame ring gasket from Andover Norton, re-torqued after heat cycle on bench, then again after 50/100/200 miles. Just wanted to be sure to be sure!!

In my quest to find the leak I've re-torqued & removed the nuts/washers from the 5/16th studs & used Hylomar on them to help seal them. I also used loctite on the studs going into the barrel when I was rebuilding the top end.

I also put some Hylomar on the two long underside nuts at the front & the nut & the rear in the middle.

I've had a good look around the head/barrels with magnification & everything is dry. I did a talcum powder 'test' on the rocker covers & the oil feed lines going into the head & they are all dry, so I'm as positive as you can be that nothing is dribbling down from the top of the head.

I've also checked all around the head gasket & it's dry, all the fins are dry all the way around. I can see the tops of the 5/16th nuts & they are dry & there's no oil on the long nuts that bolt underneath at the front.

I'll do another re-torque. Just to be sure, my plan is to back off each fastener one by one & re-torque as I go,?

It's not a major leak, I could just live with it & wipe it with a rag now & then but I'd like to know where it's coming from!!

Also it's not coming from the base gasket, on a previous bench test I put talcum powder around the base gasket + nuts & I could see a small amount of oil coming from

What's left? Can anybody suggest anything else to inspect? Could it be the centre bolt? I don't think oil is near this bolt?

I've attached a few pics after a 50mile spin, it was clean & dry before I started out.

As I said everything is bone dry on the head and the fins & the head gasket are bone dry. I'm checking the rear nut again between the carbs but it's also bone dry?

I love a good mystery, don't you?

Hi Click,
My barrels had the break through into one of the pushrod tunnels where the stud threading came through the wall slightly. I saw it with a flashlight before assembly. I gooberd around the stud with Motoseal compound, but still have a slight 3rd fin oil leak. I am also having some seepage out of the front rocker covers, even though they have been sanded flat. Just my $.02.

Tinkerbell said:

Hi Click,
My barrels had the break through into one of the pushrod tunnels where the stud threading came through the wall slightly. I saw it with a flashlight before assembly. I gooberd around the stud with Motoseal compound, but still have a slight 3rd fin oil leak. I am also having some seepage out of the front rocker covers, even though they have been sanded flat. Just my $.02.

Click to expand...

Thanks Tinkerbell (great nickname!!)

Appreciate the reply.

I'll see if I can notice anything on the pushrod tunnels, it's difficult to see anything while it's all assembled , the bike is running so well I'm not going to strip the engine for something like this. I'm going to double check all the rocker covers & oil lines but I did test them all about 100 miles ago on the bench & didn't get any leaks/weeps from anything.

Tinkerbell said:

Hi Click,
My barrels had the break through into one of the pushrod tunnels where the stud threading came through the wall slightly. I saw it with a flashlight before assembly. I gooberd around the stud with Motoseal compound, but still have a slight 3rd fin oil leak. I am also having some seepage out of the front rocker covers, even though they have been sanded flat. Just my $.02.

Click to expand...

I had a similar problem, unfortunately not uncommon, particularly on RH4 heads, I de-greased the particular area with brake cleaner, and applied Loctite 290, this type of loctite has capilary properties, and penetrates the crack, although I initially had my doubts about this method, it is still holding up well after a couple of thousand km's . A reed valve type breather may also help here.

Hi Click, are you sure the oil is coming down from the head area, and not up from the barrel base somewhere?
From what I can see in the pictures, are you sure it's not coming up from the centre front stud in the barrel which has a through hole into the crankcases?
Don't forget it will blow around and migrate when you are using the bike.

From the picture, it looks like you might have had your cylinders sleeved. If so, that might be the source of the weeping.

If so, I've had good results with 920 kits at applying Locktite penetrating sealer (the same 290 that Peter R mentioned above) to the edges of the area where the cylinder casting has been bored through.

Ken

+1 on the stud breaking through into the pushrod tunnel. This is quite common. I sealed my breakthrough with JB Weld and
used thread sealer on the stud. I also installed a reed valve breather. No engine leaks at all!!!

Mine looks like that. It’s leaking from the rocker shaft gaskets.

I just stopped being annoyed by my leak.... Not worth a coronary and not that bad anyway. I squirt it with water or whatever when it catches my attention to wash it away for a bit.

swooshdave said:

Mine looks like that. It’s leaking from the rocker shaft gaskets.

Click to expand...

Thanks for the suggestion, already checked, not coming from the rocker shaft gaskets.

Peter R said:

I had a similar problem, unfortunately not uncommon, particularly on RH4 heads, I de-greased the particular area with brake cleaner, and applied Loctite 290, this type of loctite has capilary properties, and penetrates the crack, although I initially had my doubts about this method, it is still holding up well after a couple of thousand km's . A reed valve type breather may also help here.

Click to expand...

Hi Peter,

Many thanks for the suggestion, I'll track down some Loctite 290. I already have a read valve, it's the CNW/Jim Comstock type that replaces the large nut with the oil gauze on the underside of the crankcase.

Reggie said:

Hi Click, are you sure the oil is coming down from the head area, and not up from the barrel base somewhere?
From what I can see in the pictures, are you sure it's not coming up from the centre front stud in the barrel which has a through hole into the crankcases?
Don't forget it will blow around and migrate when you are using the bike.

Click to expand...

Hi Reggie thanks for the suggestion. I did a test when this first started & cleaned the entire area. Put the bike on the bench & put talcum powder all around the area. After a while I could see spots of oil in the recess I posted a picture of. No oil spots anywhere near the barrel nuts of gasket, so I'm as positive as I can be that it not coming from that area.

lcrken said:

From the picture, it looks like you might have had your cylinders sleeved. If so, that might be the source of the weeping.

If so, I've had good results with 920 kits at applying Locktite penetrating sealer (the same 290 that Peter R mentioned above) to the edges of the area where the cylinder casting has been bored through.

Ken

Click to expand...

Hi Ken, I initially thought this myself but I asked Jim Comstock how he installed the liners and he used, I think, JB Weld to help seal the liners in the barrels. It previously had a 920 conversion hence the breakthrough in the barrels. Jim had to custom machine some 880 pistons to fit my oversize gudgeon pins from the 920 conversion. I'll try the 290 all around the area the liners break through. Thanks for the suggestion

lazyeye6 said:

+1 on the stud breaking through into the pushrod tunnel. This is quite common. I sealed my breakthrough with JB Weld and
used thread sealer on the stud. I also installed a reed valve breather. No engine leaks at all!!!

Click to expand...

I'll look into this but don't want to pull anything apart just yet for such a small leak, I'd rather just use the bike as long as I'm not causing any damage to it. Just need to keep an eye on the oil level!! Good to know it can be made leak free

jbruney said:

I just stopped being annoyed by my leak.... Not worth a coronary and not that bad anyway. I squirt it with water or whatever when it catches my attention to wash it away for a bit.

Click to expand...

Now there's a man after my own heart in the big scheme of things it's not a major issue. I've got some great suggestions as usual from everybody on this forum, so if/when I have to remove the head I'll have a look at the pushrod tunnels & in the meantime I can try the loctite 290 around the liners that breakthrough the barrels and see what happens!

Ooh! I hadn’t realized that the barrels had been bored for liners.
now I see it. To each their own! I’d be in the market for new barrels.
jusy my preference, not saying the existing situation couldn’tbe sealed up. Good luck.