Chip's '72 Combat project

Back to work!

Just back in after a 3-week road trip to 2 races and several tourist spots, so it's back to work on Chip's bike.

This phase should be interesting, we're getting down to basically the details and cosmetics, then some serious road testing.

Plenty of pix, and project wrap-up details including complete parts & modifications listings to come.

Back from a 3-week racing trip, time to get back to work. Got the decks cleared and hoisted the bike up on the stand-

Sure enough, the head gasket was damaged somehow. I thought I was being careful , but perhaps one of the new stainless headbolts grabbed the edge of the flame ring and damaged it to the point that it was a failure waiting to happen.

I'll have the machinist re-check the surfaces of the head & jugs to make sure they're okay, then re-install with a solid copper gasket and some copper seal. That's what I always used before this job, but decided on the flame ring on others' advice.

GOOD THING it happened here in my driveway, and not in Florida on some back road! (Thank God for small miracles)

GrandPaul,

Unless it's an optical illusion, that gasket looks like it doesn't quite line up properly. I have seen this kind of problem on some (not all) 750 aftermarket flame-ring gaskets. The holes are slightly off and when you screw the bolts in the fibrous material puckers and keeps the head from being seated properly. Oddly, I have never seen this issue with an 850 gasket. I always use 750 gaskets from Andover Norton.

A good flame ring gasket is easier to get a seal than an annealed copper one in my experience. However, many prefer the copper.

Actually, I had two to choose from, this one aligned MUCH better than the other one.

I may take a second look at the other one and dress the holes for proper alignment, but this incident has me shy...

I use genuine Andover Norton gaskets and have never had a problem.

Debby

grandpaul,
It looks to me those stainless steel bolts have given in to the combustion pressure and the gasket has blown out.

Weeeeee.... those soft stainless steel bolts and replace them with standard high tensile norton bolts. You can never be sure what grade of stainless has been used. High tensile stainless is a beggar to machine and polish, and is bloody expensive.

And fit a genuine Norton head gasket, a Reinz ( I think that's how you spell it) and you shouldn't have a problem.
Best of luck,
Cash

I've always been suspicious of stainless steel fasteners for use on engines. They don't seem near strong enough to me.

For instance, most 300 series stainless has a minimum yield strength of around 36,000 psi. In contrast, a grade 5 carbon steel bolt (typical hardware store variety) has a minimum yield of about 90,000 psi.

Andover gasket ordered.

The stainless bolts are the high end parts from Old Britts, VERY highly reputed, and well suited to the task.

While the head gasket is winging it's way over, I got the bodywork fitment complete. Just need to CAREFULLY drill the windscreen and mount
it up. Good clearance from handlebars, but slightly limited steering at the far ends of the travel (as Chip said it was before).

It won't be much longer now...

Grandpaul,
You probably already know this, but drilling windscreens requires a bit with a sharper angled point (90 or even 60 degree). These are available from Gustafson or Craftcs.com.

Here's a link worth reading http://www.bertram31.com/proj/tips/drill_acrylic.htm

hee hee

Ron, I know ALL TOO WELL!!!

I just drilled the one on my Combat back in early May.

I had a spare windscreen with one small crack (guess when that happened?) that I was using, but it blew off while the bike was strapped to my open trailer, on the way home from a bike show; I had forgotten to tighten the screws and put a dab of silicone on the ends of the screws! It was a total drag, because the crack was very small and I intended to save the new screen for much later.

Drilling slowly and with next to zero pressure on the drill are the other two tips that pay off.

I went back and noted that the head gasket I pulled off during the tear-down was a solid copper one, the ones I ALWAYS use on my Triumphs.

Hmmmmmm.....

Worst case, I'll give the new flame ring gasket a careful try-out; anything suspect, I'm going back to my favorite tried-and-true method with the solid copper gasket that came in the Wassell Combat gasket set.

Went ahead and polished the oil pump plates JUST IN CASE. The pump shaft had a bit of end float, the book says that's the thing to check. I carefully reworked the plates and re-assembled it to the absolute minimum perceptible play in the shaft with a good snug rotational feel.

I wish you the best of luck with the head gasket, but you really want to consider dumping those stainless steel head bolts.

I've just put my old girl back together using a Reins head gasket and HTS bolts. I've done a couple of hundred miles and found one nut needed a 1/4 turn the rest OK with no signs of leaking. I'll check again as usual.

The motor compression is tad under 9.5 : 1 with a 3s cam etc.

Cash

This-



Is in here now-



I'm taking a lunch break, then I'll have it all nipped back up by this evening, maybe give it a test ride if it's not too late.

ONE KICK!

(Well, that shouldn't suprise anyone, me least of all)

I'm going to stick a few more parts on it for a test ride, so as not to arouse the suspicion of the local constabulary.

Not just YEAH!, but HECK YEAH!

Believe it or not, I think I can feel the difference in the additional .020 overbore. This thing is a freight train, and it's not even strobe timed with the carbs fine-tuned yet! Almost felt like the front tire was getting light on brisk accelleration (nothing harsh).

Front brake feels excellent; way better than stock. It settles right into the left-right-left lean angles on our private drive at about 40 MPH, I think I ran it up to 55-60 once or twice and that's at about 1/4 throttle. Suspension is nice over relatively easy bumps and small pavement irregularities, should be more than adequate when adjusted for rider weight, etc.

No wobbles, wiggles or niggles; just nice and stable.

I'm going to put my Combat's plate on it, mount the fairing & lights, and take it out on the highway and the Loop; about 20 miles round trip, all in the city (just in case).

Just took a very nice 20 minute ride out on the Loop, after strobe timing the engine to spot-on 28 degrees BTDC @ 5,000 RPM on a hand-held tach.

There is a nice stretch close by the house that is about 3/4 mile long with side traffic from only one intersection that you can see clearly from the starting point, no buildings for at least 250' back from the intersection. I waited until traffic cleared in my direction and no more traffic coming from behind all the way bach to the signal about 1/4 mile up.

Without abusing it or hammering the top end, I applied a generous amount of throttle with just the right clutch release to avoid either slippage or a wheelie, and launched like a jetliner. I have yet to install the instrumentation, but I sure caught up with traffic by the time I was just about to shift into 4th. I'd estimate 75 - 80. I'm fairly certain that it was at less than or just about 1/2 throttle.

I could have been hands-off if I had a throttle lock, it tracks perfectly straight and true; no weave, oscillation or squirrliness whatsoever. Lane changes are a "just think about it, and it happens by itself" kind of thing.

The seat is not exactly cushy, but this is a 70s thoroughbred, not a 2-wheeled easy chair.

I think the front brake master cylinder sleeving & braided stainless line might be something to consider for regular use at the upper edges of the bike's envelope.

My biggest concern now is how to deal with the high compression, as the heat-soaked engine started to protest the relatively low octane modern mid-grade that I have in my tank. I'm not so sure Premium is going to clear it up completely, so I need to look into appropriate timing and carburation adjustments to get the best compromise.

All in all, a very fun ride and guys were all checking out the bike as I cruised through the subdivision on the way home. Maybe it was because the bike has no lights and plate, or maybe because it's a cool looking bike; it looks like a raw Bonneville racer right now.

Bodywork & lighting next!

"For better or for worse"

I raised the needles one notch, re-torqued the top end & snugged up the exhaust nuts and took the bike out for another loop.

Boy, howdy did it feel even better, and NO CLATTER on hard accelleration. Just what the doctor ordered on carb adjustment.

Then, I gave it a hard pass on the half mile straight and got a major scare! The bike was acellerating beautifully and then, right as I shifted into 4th, it just flat DIED. I tried checking to make sure I didn't run the tank dry (nope), the key hadn't vibrated to the off position, the wires were still atached to the right coil, then I looked at the LEFT coil, and there was the ground wire, dangling. I had already called a buddy to come fetch me, so I called him back and told him thanx anyway.

I thought the ride home would be uneventful, then I started hearing what seemed to be a compression leak! Turns out I had failed to nip in the tangs that hold the exhaust nut keepers back in after re-tightening.

YEEF!

It's all good now. Glad there were no actual issues, just stupid little stuff. That's exactly what these shake-down runs are for. I've got the oil weepage cut in half after the re-torque, now to apply a bit of thread sealer on the crankcase breather bolts & gasket, and one or two other spots, and it should be ESSENTIALLY leak-free.

Our discussion about adding the timing chest breather will result in that being done today or tomorrow as well. Not much left to do!

Prepped the tank, masked the filler neck-



Here's how the acetone came out-



Tank washed out nicely, and allowed to dry over lunchtime.

Donned the proper gear, mixed the proper portions, poured it into the tank and CAREFULLY juggled the tank for about 12 - 15 minutes 'till my back couldn't handle it any more. I'm sure I got a great solid coat on it, then drained off the excess. hard to see, but it's all nice and glossy in there now-



I'm going to let it dry out and cure really well, several days, and trim up the filler neck nice and clean before installing the new cap & taps. It will be the last item to go on the bike.

Grandpaul,

What brand tank liner are you using?

Thanks,

Jason