Kibblewhite High Performance Pushrods (2017)

I used Kibblewhite High Performance Pushrods in my 750. Top of one of the pushrods disintegrated. See photo. What are the best high performance push rods to use? I dont think I will use these anymore.

My thought process would be:

New std AN
Custom alloy from Comnoz
Maney lightweight steel

That’s not in order BTW, but it’s what I’d be comparing.

I have a set of the Kibblewhite's that I was intending to use. I wonder if this problem has happened to others.
Jerry, have you contacted Kibblewhite?

Ed

Ouch! I only recently noticed that Old Britts was selling Kibblewhite pushrods, along with the stock AN rods and my Left Coast Racing ones that he has carried for some time. I hadn't realized Kibblewhite was making Commando pushrods. The design looks a lot like the (no longer available) Alloy Tech items I used to use. The cup end looks less robust than either the stock ends or the Smith Brothers and CompCams ends I use. On the other hand, I never had any failures with the Alloy Tech ends on the race bikes.

If you are using standard length pushrods on a typical street Commando, I don't think you can really do any better than the stock Commando pieces. I only started making my own because I wanted to be able to make custom lengths, as well as the double cup end style for use with BSA lifters. But they are about the same weight and strength as the stockers. Making my own also lets me experiment with other materials and tube dimensions, but that's really only of value for high performance engines with higher spring pressures and higher rpm needs, like the ultra short stroke engines we're now seeing.

As usual, just my humble opinion, not casting any aspersions on the 4130 and titanium push rod fans out there.

Ken

I am not going to contact kibblewhite as cannot be bothered. I will probably put stock ones in...

i use these in my triumph 650 LSR machine. i've never had a problem, and i've spun the motor to over 9000 with them.

lol. not on purpose.

i tried carbon fibre ... one broke. Though they were not from him ,Steve Maney made the observation that c/f rods would require little or no gap.. he suggests that his lightweight steel ones are run with half the standard clearence because of the different coefficient of expansion... what are the kibble white made from? The important thing with push rods is rigidity... and yes the c/f were great for all of a few hundred miles ! Have yet to lift the head to put Steve's in but am sure they will be well worth it even with a standard cam

Jerry,
I am running kibblewhite push rods in my 850 but using a Megacycle cam which is milder than your set up (12a??? I'm guessing) so far I have +25,000 miles on the engine with no issues. I wonder if it was just a bad fluke?
Cheers
Thomas

Use the stock ones.

ive always liked the stock units.

Ken was kind enough to give me some pushrods that he made. I really like them. I have the head back on the bike and eveything sounds perfect. I need to go for a decent ride to test it. I now have new rearsets too,I iwll post some photos later.

Guinness pushrods... cool!

CanukNortonNut said:

Jerry,
I am running kibblewhite push rods in my 850 but using a Megacycle cam which is milder than your set up (12a??? I'm guessing) so far I have +25,000 miles on the engine with no issues. I wonder if it was just a bad fluke?
Cheers
Thomas

Click to expand...

Yikes, I see pictures on FB of an engine that was destroyed and it seems to be linked to a failed Kibblewhite push rod cup.

I have these in my unstarted engine, should I be worried ?

Any more failure or no problems reports, pulling the engine back out to change them , yikes.

I swapped out the KPMI rods pictured by Jerry with the black Chromoly version they also sell, no issues thus far

This would be my concern.
To thin from the cup shoulder to inner radius ? or to hard (Rc) or a combination of both.

Bending push rods, sure, cups disintegrating, not even if there was spring coil bind.
Of course something has to apply enough pressure to initiate fracture, perhaps mismatched adjuster ball to cup radius.

Only time I’ve seen similar happen is with Wassell pushrods in a Triumph. The radius of the cup didn’t match the ball on the rocker, it was too small, thus the ball didn’t seat fully in the base of the cup, thus excessive load was applied to the sides of the cup, causing one to fail like that.

Time Warp said:

Yikes, I see pictures on FB of an engine that was destroyed and it seems to be linked to a failed Kibblewhite push rod cup.

I have these in my unstarted engine, should I be worried ?

Any more failure or no problems reports, pulling the engine back out to change them , yikes.

Click to expand...

Hey Les - I discussed pushrods with JC and Tony @ AeroMachinists when redoing my motor a few years ago, and their recommendation was to stick with my stock ones as they were in good condition fine for the 312a and conical springs I had from JC. We discussed higher perf alu and steel pushrods, but that was overkill for the needs of the motor.

What cam do you have in your new motor?

There is some discussion of pushrod choices here in this thread - https://www.accessnorton.com/NortonCommando/cam-followers-andover-to-the-rescue.29036/

gortnipper said:

Hey Les - I discussed pushrods with JC and Tony @ AeroMachinists when redoing my motor a few years ago, and their recommendation was to stick with my stock ones as they were in good condition fine for the 312a and conical springs I had from JC. We discussed higher perf alu and steel pushrods, but that was overkill for the needs of the motor.

What cam do you have in your new motor?

There is some discussion of pushrod choices here in this thread - https://www.accessnorton.com/NortonCommando/cam-followers-andover-to-the-rescue.29036/

Click to expand...

Stock (NOS) camshaft David.

JS Motorsport = no stock type push rods.
Steve Maney by bank transfer only payment
Andover Norton show push rods out of stock.
I will go through that thread....

I will pull the engine back out of the frame once the heady steady is finished and find a push rod source ASAP. ( Or could simply refit the stock ones I have )
I sourced the KB valves / springs / retainers / collets / push rods from JC, the KB items might be fine (but look very thin through that shoulder where they failed) but can not take the risk over $200 parts in a $20k bike.


The engine on FB (600 miles in fully rebuilt, 73 750) ended up with bits (maybe from the fractured lifter cups) jamming the scavenge gears it seems, the oil pump shaft then sheared off followed by piston seizure including split connecting rods that other wise stayed together, total carnage all the same.

Time Warp said:

Stock (NOS) camshaft David.

JS Motorsport = no stock type push rods.
Steve Maney by bank transfer only payment
Andover Norton show push rods out of stock.
I will go through that thread....

I will pull the engine back out of the frame once the heady steady is finished and find a push rod source ASAP. ( Or could simply refit the stock ones I have )
I sourced the KB valves / springs / retainers / collets / push rods from JC, the KB items might be fine (but look very thin through that shoulder where they failed) but can not take the risk over $200 parts in a $20k bike.


The engine on FB (600 miles in fully rebuilt, 73 750) ended up with bits (maybe from the fractured lifter cups) jamming the scavenge gears it seems, the oil pump shaft then sheared off followed by piston seizure including split connecting rods that other wise stayed together, total carnage all the same.

Click to expand...

Very sorry to hear all that.

Very disapointing.

Time Warp said:

Stock (NOS) camshaft David.

JS Motorsport = no stock type push rods.
Steve Maney by bank transfer only payment
Andover Norton show push rods out of stock.
I will go through that thread....

I will pull the engine back out of the frame once the heady steady is finished and find a push rod source ASAP. ( Or could simply refit the stock ones I have )
I sourced the KB valves / springs / retainers / collets / push rods from JC, the KB items might be fine (but look very thin through that shoulder where they failed) but can not take the risk over $200 parts in a $20k bike.


The engine on FB (600 miles in fully rebuilt, 73 750) ended up with bits (maybe from the fractured lifter cups) jamming the scavenge gears it seems, the oil pump shaft then sheared off followed by piston seizure including split connecting rods that other wise stayed together, total carnage all the same.

Click to expand...

Yeah, saw that thread. I agree, not worth the risk given this thread too.

I wouldn't hesitate to inspect and fit the old stock pushrods.