Top end teardown 73 Bonneville

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Had to pull the head on the Triumph today. Unfortunately, the right side spark plug blew out and stripped the threads. I figured I would post a couple pictures of the internals. Unfortunately, I didn't think to get a picture of the bottom of the head before it was was off to the machinist.

73 Bonneville - 66k. Most of it's life with 20w50 Castrol, the last 4 years on Mobil 1 5w50.

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Soaking the pistons with MMO in the meantime to try and get a little more carbon off. We don't have ethanol in our gas at all in my state so it's interesting to see the effects compared to some e10 bikes. Not very much carbon. A little more so on the left side which makes sense because before I went to the electronic ignition, that side always had a weaker spark.

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This bike has had some gasket overhauls but is still the stock bottom end.
 
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Thanks for the pics! I'm curious what the combustion chambers look like.

I actually clicked on the topic thinking it was about a Pontiac bonneville 455.
 
You both clicked the link thinking it would be a Pontiac in the Motorcycle section? LOL


I didn't think of getting a picture of the combustion chamber before sending it off. I may be able to get one before anything is cleaned off of it before the work is done.
 
Originally Posted by jayg
You both clicked the link thinking it would be a Pontiac in the Motorcycle section? LOL


I didn't think of getting a picture of the combustion chamber before sending it off. I may be able to get one before anything is cleaned off of it before the work is done.


I clicked on the left hand topic bar ( recent topics), it does not list the section, just the topic.

Top end teardown 73 Bonneville
by jayg. 10/14/18 08:35 PM

Still , i love the pics. I love to see pics of things i've never worked on before. Thanks again.
 
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Originally Posted by rubberchicken
How are you going to fix the head ? Did you find a replacement, or do you have to get this one helicoil'ed or welded ?


Likely a time sert with some other head work being done at the same time.
 
Been into those engines countless times, it was my life in the '70's, but never pulled the top end off a 10 stud, they were too late model for us. Interesting to see the casting is still made to accomodate the 8 stud head. We used to see the occasional ''9 stud'' 8 stud head and sometimes barrels too...the unit barrels had an oil feed to the exhaust followers.
 
I rode a vertical twin English 30 cu in machine while in college back in the 60s.I forgot the manufactures name but, the model was the 30.50 Chief. I still favor the sound of those engines. I am too old to ride safely anymore due to reflexes at 80 years old. Ed
 
Nice bike, thanks for posting. I have a ‘66 that used to be my daily rider. Been collecting cobwebs for a few years now and I need to fix that this winter.

Are you going to replace the valve guides while it's apart?

I added a Boyer ignition and an aftermarket voltage regulator. Once I got rid of everything I could that had Lucas printed on it the bike has been rock solid reliable. Rode it across the US years ago with only a chain replacement along the way.
 
Originally Posted by spasm3
Originally Posted by jayg
You both clicked the link thinking it would be a Pontiac in the Motorcycle section? LOL


I didn't think of getting a picture of the combustion chamber before sending it off. I may be able to get one before anything is cleaned off of it before the work is done.


I clicked on the left hand topic bar ( recent topics), it does not list the section, just the topic.

Top end teardown 73 Bonneville
by jayg. 10/14/18 08:35 PM

Still , i love the pics. I love to see pics of things i've never worked on before. Thanks again.
same
 
Originally Posted by Langanobob
Nice bike, thanks for posting. I have a ‘66 that used to be my daily rider. Been collecting cobwebs for a few years now and I need to fix that this winter.

Are you going to replace the valve guides while it's apart?

I added a Boyer ignition and an aftermarket voltage regulator. Once I got rid of everything I could that had Lucas printed on it the bike has been rock solid reliable. Rode it across the US years ago with only a chain replacement along the way.


This bike also has the Lucas removal mod. Haha

Pazon electronic ignition and podtronics regulator.

I'm leaning toward valve guides while I'm in there but I'll see how they check out.
 
I rode that exact same bike (with lower bars) for years. Same color, exhaust and all. Other than buzzing your hinie to sleep on the freeway, it was a great bike. Friend still has it back in Maryland.

They were a runner, and a canyon beast. Decent Avons and nothing much could stay with you in the corners. Two up they'd float the front wheel through intersections off a light like nothing
laugh.gif


Sold mine to my bud and kept the RD-400 that I had at the same time
laugh.gif


Love right side sifts. Have looked at a few used ones since, but the prices are nuts ...
 
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Originally Posted by BrocLuno
I rode that exact same bike (with lower bars) for years. Same color, exhaust and all. Other than buzzing your hinie to sleep on the freeway, it was a great bike. Friend still has it back in Maryland.

They were a runner, and a canyon beast. Decent Avons and nothing much could stay with you in the corners. Two up they'd float the front wheel through intersections off a light like nothing
laugh.gif


Sold mine to my bud and kept the RD-400 that I had at the same time
laugh.gif


Love right side sifts. Have looked at a few used ones since, but the prices are nuts ...


They're fun and though it's my "bigger" bike, it's smaller than just about every other street bike these days. Once I think about it, I actually don't even have a left side shift bike at the moment.
 
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