What is this?

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solarmoose
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What is this?

Post by solarmoose »

Bought a 79 a while back in November and took it for a ride the next spring. It ran great but then the engine stopped running
as I was pulling into the driveway and refused to restart. Did not have time to work on it and it has waited for a year before
I now have time to investigate. Battery good and starter turns motor over plenty fast, found spark on #1 cylinder (front left?)
but it was dry. Gas is leaking out of carbs, I think from around the bowl gaskets but after a couple days it is leaking from fewer
places. I'm hoping the gaskets swell back up so I can continue diagnosing problem. Clearly I'll need to pull the carbs for rebuild.
I have Nixon's booklet and shop manual. I'm going to try and get gas through the plug holes just to see if it'll fire up before
I pull the carbs.

Question: Each carb has a red device that takes the carb overflow tube and connects to the bottom of the carb mouth as
seen in the photos. I note the airbox rubber fitting does not have the clamps and it appears the airbox rubber has been
modfied slightly too. What is this red fitting and why would it be used?
My inclination is to remove it and return the hoses to stock. I doubt this has anything to do with why it quit running but
I really don't know.

Image

Image

steve murdoch icoa #5322
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Re: What is this?

Post by steve murdoch icoa #5322 »

Stock is almost always better.
Never seen that alteration before.

daves79x
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Re: What is this?

Post by daves79x »

Looks like some version of an old Dial-A-Jet system.

Dave

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solarmoose
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Re: What is this?

Post by solarmoose »

Another clue: They have R.P.O. a patent # and MADE IN THE USA stamped on them. Going to take better eyes than mine
or a magnifying glass to read the patent #. There is a screw in the bottom. Time to disassemble.

Interesting thought about dial-a-jet. We used to use them and Holz altitude compensator on sleds before the days
of factory altitude compensator systems and FI. If I recall the dial-a-jet went through the bowl drain to change the main jet.
Holz Engineering made an altitude compensator that varied float bowl pressure and was remotely adjustable.
Cool system as long as you kept an eye on the EGT...
This bike was originally sold in Anchorage, sea-level town and none of the highway passes are above 3,000 ft.
Any more ideas?

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Re: What is this?

Post by solarmoose »

Went from bad to worse.

Still won't start even with fuel down the plug holes. Checked compression, nearly zero on all but #1 and it was only 60psi.

So I pulled the valve cover off. Cam chain is broken. Appears that a few valves are open even though lobes are up.
This must be an interference motor? Bent valves?

More damage than I'm capable of repairing and no CBX experts in my neighborhood.
Disappointed to say the least. Was hoping to ride this one this summer. The rest of the bike is in very nice shape
and not a lot of miles.

Any recommendations for repair shops for a quality engine rebuild? Only one I'm familiar with is Tims.

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Re: What is this?

Post by tevan »

Preston

daves79x
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Re: What is this?

Post by daves79x »

Which cam chain broke? If it was the long one, then someone had just worked on the engine and installed the cams wrong. Any other cam chain breakage is almost unheard of.

The head will be too expensive to repair compared to what you can still buy a used one for. Every valve that is bent will also have a cracked guide. The last head I saw with a broken cam chain had 16 bent valves and 15 cracked guides. Guide replacement and cost of valves can get you into well over $1000 for just that. Cases will need split to replace the cam chain and inspect for other damage. How high were you revving when the bike quit?

Sorry for your bad luck, but it is fixable at reasonable cost if you dig around and find a good used head. Your location doesn't help you much either! Let me know if I can help you.

Dave

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solarmoose
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Re: What is this?

Post by solarmoose »

Dave,
It broke the long chain.

Image

And you can see in the photo it had two places of failure. The engine was running well and I had taken it out for my first ride,
didn't run it hard and was coming into the driveway when it died, so no, not high reving. I'm the fourth or fifth owner, don't know
the previous history. This has taught me that taking on a bike with unknown history requires a thorough go-over it before riding it.

Is it possible the cam chain tensioner was too loose allowing the chain to climb over the gear?
How would installing the cams wrong have caused this?

Certainly as you say the damage is extensive. Not sure what my plan to repair will be, but it will be repaired.

Image

David

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Re: What is this?

Post by Rick Pope »

Solarmoose,

I will be in your neck of the woods in July. I don't know if I can help with shipping, but I have plenty of space.

I'd be glad to help.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

daves79x
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Re: What is this?

Post by daves79x »

Check the cam timing and I'm sure you'll find them 180 degrees out. Otherwise, a catastrophic tensioner failure - very rare.
Dave

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solarmoose
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Re: What is this?

Post by solarmoose »

Rick Pope wrote:Solarmoose,

I will be in your neck of the woods in July. I don't know if I can help with shipping, but I have plenty of space.

I'd be glad to help.
Rick,
Thanks for the offer. I may take you up on that.
Planning to be in Fairbanks? You're welcome to stop by the shop for coffee/beer or whatever if you have time.
David

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Re: What is this?

Post by Rick Pope »

Rick,
Thanks for the offer. I may take you up on that.
Planning to be in Fairbanks? You're welcome to stop by the shop for coffee/beer or whatever if you have time.
David
Yes, we'll be in and around Fairbanks for a few days. And will for sure make time to visit.

Planning to ride the dual sports to the Arctic Circle, do some local sight seeing, and head down to Denali for a few days too. Will need a recomendation of a campground that can handle a semi/camper.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

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