JBWeld hole plugs

jug · Apr 2, 2015

I am rebuilding my 750 engine after an expensive brain fart caused it to expire. I am up dating a few things, like JS internals etc and while Im at it, I'm fitting one of Matt's (CNW) breather gizmo's. I have several holes I need to plug in the timing side case. CNW uses threaded plugs (see pic) but wondering if JBWeld could be an option.
Thanks in advance.
JUG

Fast Eddie · Apr 2, 2015

I also went for threaded plugs. I thought abut JB weld etc, but then realised, if its all down that far, why not do it right... and why risk something like a JB weld plug coming loose??

What Spec of JS internals are you going for?

Here's my plugged timing chest:

jug · Apr 2, 2015

Got a set of his bush less carrillo rods, Stock spec radius cam kit is on its way. Light weight 750 stock pistons with gapless rings to suit, and beehive valve set. Plus his CR carb setup.
JUG

Hobot · Apr 2, 2015

hobot wouldn't hesitate to fit slightly undersized alu plugs glued in with original hi temp *slow set* JB cold weld with surfaces roughed up a bit. There is nil force to resist and JBW can tolerate the thermal expansion contraction as slightly softens about 300' F. Another alternative w/o any back up plug needed is the Iron Putty tube type epoxy which has plugged countless cases and shells and oil pans and brackets. Still not as throughtful steam punk finished looking as well done threaded and staked plugs.

cjandme · Apr 2, 2015

jug said:
Got a set of his bush less carrillo rods, Stock spec radius cam kit is on its way. Light weight 750 stock pistons with gapless rings to suit, and beehive valve set. Plus his CR carb setup.
JUG

Nice, That's money well spent if you ask me, jug. :wink: I'm jealous.... :mrgreen:

concours · Apr 2, 2015

For a $20 tap, why would you risk it?

comnoz · Apr 2, 2015

I have done a few of them using slightly tapered aluminum plugs that were a snug fit in the holes. I installed the plugs with JB weld and they have caused no issues. I use this method when the engine is assembled and in the bike. Jim

CanukNortonNut · Apr 2, 2015

You can get these plugs at Home Depot with an NPT tap and some Red Loctite or JB if you choose will close the holes up.
My 5 cents.
Tom
CNN

jug · Apr 3, 2015

Thought about welding them up but worried about distortion. Looks like the plugs have it

jug

jug · Apr 3, 2015

Fast Eddie said:
I also went for threaded plugs. I thought abut JB weld etc, but then realised, if its all down that far, why not do it right... and why risk something like a JB weld plug coming loose??

What Spec of JS internals are you going for?

Here's my plugged timing chest:

Good job.

Peter R · Apr 3, 2015

Excuse me for my ignorance, but what is the benefit of plugging these holes ?

Fast Eddie · Apr 3, 2015

Peter R said:
Excuse me for my ignorance, but what is the benefit of plugging these holes ?

Only of any benefit when using a reed valve breather located directly in the crankcase, with one of these, the theroy is to minimize the amount of chamber avaialble to 'store' the gases. By doing this, and having a one-way reed valve, the engine breathing is optimized.
As standard, my engine breather acted like a pump, pushing and pulling 850ccs of gas back and forth with each stroke, which was all clearly evident in the oil tank. With a Comstock reed valve, there is hardly any detectable gas movement out of the tank vent.
There are two versions, either the version that screws into the sump plug (like I have) or the version that bolts to the back of the case like the one towars the bottom of this page: http://coloradonortonworks.com/part-categories/engine/

Peter R · Apr 3, 2015

Thanks for your explanation Eddy, much appreciated.

dragonfly · Apr 3, 2015

I think this mod plus was one of the best improvements I've done for my Commando. The addition of Jim's breather plus moving the oil scavenge rearward is well worth the effort imo. No more oil on my garage floor.

CanukNortonNut · Apr 3, 2015

dragonfly said:
I think this mod plus was one of the best improvements I've done for my Commando. The addition of Jim's breather plus moving the oil scavenge rearward is well worth the effort imo. No more oil on my garage floor.

+1
I did the comnoz mod on my 850 and this was money well spent. no more oil coming out of the tach drive housing which was still happening with the XS650 reed valve that I tried at first.
Cheers,
Tom
CNN

JBWeld hole plugs

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