'71 leaky head gasket teardown reveals bigger problems

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Curious to know if anyone else has JCC pistons with round wire clips instead of the snap ring eyelet clips?
 
Yes, that funny depression just toward center of the valve pocket looks like it isn't standard.
if the pistons are in the wrong cylinders, with the valve cut outs in the wrong place-then yes the valve will kiss the piston and make is own indentation!
 
Curious to know if anyone else has JCC pistons with round wire clips instead of the snap ring eyelet clips?

I'd think Jim Comstock (comnoz) would know.

(JCC replacement pistons for other makes of motorcycle can have wire circlips so this is specifically about JCC Norton Commando pistons)
 
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Surely who ever done the work would have made sure they had the right piston for where the valves are for the valve pockets, he must have forgotten to put his eyes on (glasses), I be pulling that motor down to make sure anything else hasn't been done wrong with it, must have been a reason why pistons had been removed in the first place, there are so many dishonest people around who lie about things when selling bikes or car for that matter, in the long run pulling that motor completely down might be cheaper than having something else go wrong with it.

Ashley
I see it SOOOOO often, people not checking their own work as they proceed. “Proofreading” MATTERS!
I’ll bet that was a “bike shop” that did the work too...
 
I'd think Jim Comstock (comnoz) would know.

(JCC replacement pistons for other makes of motorcycle can have wire circlips so this is specifically about JCC Norton Commando pistons)

The JCC's I bought from Jim came with snap ring circlips, you can just make them out here

'71 leaky head gasket teardown reveals bigger problems
 
I think the new JCC all come with snap ring eyelet clips. The pistons on my bike are at least 10 years old.
Whose coatings did you use?
 
Surely who ever done the work would have made sure they had the right piston for where the valves are for the valve pockets, he must have forgotten to put his eyes on (glasses), I be pulling that motor down to make sure anything else hasn't been done wrong with it, must have been a reason why pistons had been removed in the first place, there are so many dishonest people around who lie about things when selling bikes or car for that matter, in the long run pulling that motor completely down might be cheaper than having something else go wrong with it.

Ashley

Agree, and I should pull it down completely. It is difficult to determine if the cases have ever been split before. Camshaft, bores and lifters look perfect. I hope the pistons in the wrong holes were just an oversight, and that the same guy did not get into the bottom end. Will remove the timing cover for inspection.
 
I bought this '71 remotely, sight unseen a few years ago. Supposedly it had an original 4000 miles, after speaking to the original owner on the original '71 Texas title who said engine never been apart! Ha.

After its second club ride last weekend, we noticed a lot of smoke out the right hand exhaust when heavily on the throttle, and a leaky head gasket.

Here is what we found upon taking the head off.
Anyone notice anything amiss? :eek:


View attachment 8837
Pistons in wrong and intake valves touching the tops of the pistons.
 
I passed on 2 bikes prior to getting the one I have now because you could see rounded off nuts n bolts all over the engine (owner swears it's never been apart!) or the owners said "yep, rebuilt'er myself!" Yea.........no thanks.
 
Curious to know if anyone else has JCC pistons with round wire clips instead of the snap ring eyelet clips?

I recently purchased JCC pistons that came with wire clips ..... used the internal snap ring type instead.

The pistons also were mis-marked R and L (Right was marked L, etc). Perhaps this is why the PO got them reversed.

Slick
 
Ohhh. Mismarked. Wonder if they came from the master of mismarking, Nor**l? Remember that gearbox cover with the backwards numbers?
 
Even mismarked, pretty hard to believe anyone could ignore the splayed exhausts and parallel intakes.
 
Curious to know if anyone else has JCC pistons with round wire clips instead of the snap ring eyelet clips?

my circlip episode happened over 20 years ago. Here's a picture of the offending circlips in my case

'71 leaky head gasket teardown reveals bigger problems


My deduction was that the tangs on the circlips can act like bob weights to flex the clip when the piston changes direction thereby compressing the circlip so it pops loose. I think Jim schmidt also said that the center of the wristpin can also push on the tang to drive it out of the piston groove. That makes sense also. Jim Comstock also said that my circlips were good "for lawnmower engines" and thats about it.

The thing that Jim Schmidt pointed out in one of the circlip threads that made sense to me, was that if you have a round wire circlip, then a small bevel on the end of the wristpin means that the wristpin actually prevents the circlip from popping out if it pushes on it. Also, that having some sort of "tang" on a circlip gives the wristpin leverage to drive it out of the piston groove.

If I had wire circlips, I would trim off the tang on them and put a small bevel on the wristpin edge... but that's me.
 
What I find interesting is that the witness marks on the piston crowns is a good example of the conservative "one size fits all" approach that many component manufacturers take. The valve on piston crown witness marks suggest that the valve cut outs provided are way more than ample. The manufacturers and suppliers have lots to loose if a ham fisted mechanic/engine builder botches the valve pockets clearance and trashes a motor (guilt by association) so the manufacturer provides clearances that will pass a Titanic.

On the other hand, it's great to have clearance if you want to step up the game a little bit and experiment with different cams without having to customize the valve pocket clearances.


I bought this '71 remotely, sight unseen a few years ago. Supposedly it had an original 4000 miles, after speaking to the original owner on the original '71 Texas title who said engine never been apart! Ha.

After its second club ride last weekend, we noticed a lot of smoke out the right hand exhaust when heavily on the throttle, and a leaky head gasket.

Here is what we found upon taking the head off.
Anyone notice anything amiss? :eek:


View attachment 8837
 
Even mismarked, pretty hard to believe anyone could ignore the splayed exhausts and parallel intakes.

True but...

I once had a Trident engine assembled by a professional engine builder who was also a friend.

I went round to his workshop to check on progress and he was just about to fit the head, I got there just in the nick of time to spot that one piston was back to front... the other two were correct... how could he possibly not have seen that?!
 
True but...

I once had a Trident engine assembled by a professional engine builder who was also a friend.

I went round to his workshop to check on progress and he was just about to fit the head, I got there just in the nick of time to spot that one piston was back to front... the other two were correct... how could he possibly not have seen that?!

A bit like your builder who put your TSS conrods in the wrong way around with the little end offsets pointing the wrong way...lol.
 
Not a perfect world, mistakes happen. Experience and repetition probably helps. Also probably a good idea to get build progress pictures if someone else is doing the build. The good news is my valves are NOT bent. These Kibblewhite valves are strong!

About the wire piston pin clips, mine are very lightweight, and were rather easy to pull out with needle nose pliers.
I will probably buy some eyelet clips to test. First, I will need to put the pistons under a magnifying glass to check if they are compatible with the clip groove.
 
True but...

I once had a Trident engine assembled by a professional engine builder who was also a friend.

I went round to his workshop to check on progress and he was just about to fit the head, I got there just in the nick of time to spot that one piston was back to front... the other two were correct... how could he possibly not have seen that?!
Been quite a while since I had the head off a triple. Aren't the valve pockets symmetrical, i.e. parallel to the wheels?
 
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