Classic Triumph Bonneville

[Mr. Dazzle]

I got 2 new piston pins (I suppose I should call 'em gudgeon pins given the age of this bike), new pin clips, new cylinder base nuts and some new pushrods in the post this morning.

I can now restart assembly in anger! Next job is to get the pistons back on the rods. I got new pins 'cause the old ones were a bit chewed up at the ends from being removed/installed a few times. I suppose it doesn't strictly matter, the bits where they're damaged are just pressed against the piston in service and there's no relative motion. But since I'm in here....

[Mr. Dazzle]

OK so I lied...tonight's job was actually cleaning the pistons with very fine emery, 6000 grit I think it was, to get the last of the gunk off. To be fair to the guy who cleaned them up and gapped the rings, they did look like they'd been tarmaced on top when i dropped them off!

Bottom one is all clean, top one isn't. Seems like the bottom one has a bit missing though, it must have been missing for a long time. Might have to be new piston time, but at least I could give her back her 11:1s! Currently its standard 9:1, but the majority of the bikes life they were 11:1, my FiL changed them when he couldn't start it any more.



I also cleaned up the tappets and put the back in the block. The cable ties around the top just stop the tappets falling out while you're putting things back together.

[Mr. Dazzle]

Tempted by these.....perfect set of pistons for me, 11:1 ratio and +40 thou just like I need.

https://www.ebay.co.uk/p/11043515699?iid=154112048295.

Downsides - harder to start (not exactly easy to kick over already ), need to run Optimax/octane booster, need to ensure my timing is spot on.

Upsides - POWER! Makes the bike like it was when my FiL bought it as a 21 year old hooligan. This bike supposedly already has uprated cams and it's also already fitted with the hotter of the two available tappets. I dunno, seems fitting that I should get it back to the bike he rode as a young man.

[Nidge]

If it were me I wouldn’t - on a 50 year old bike I’m more interested in setting it up for reliability rather than outright performance.

[Mr. Dazzle]

Yeah the performance is nominal. If I get it really really good it might be as fast as a modern 500

It's more about 'originality' to me.

[Rockburner]

Yeah the performance is nominal. If I get it really really good it might be as fast as a modern 500

It's more about 'originality' to me.

Originality to how it came out of the factory, or how it was (ab)used when in service?

[Mr. Dazzle]

Yeah the performance is nominal. If I get it really really good it might be as fast as a modern 500

It's more about 'originality' to me.

Originality to how it came out of the factory, or how it was (ab)used when in service?

How my FiL had it....he bought it off a racer and tore around the countryside and various RAF bases on it

I've been speaking to Mrs. D about it, it's her bike after all. She has fond memories of her Dad having to literally jump on the kicker to get it going. She also asked me (unprompted) "Do they do classic bike trackdays?"

She wouldn't be the one kicking herself into a sweaty puddle when you stall at a set of lights.

[Rockburner]

Yeah the performance is nominal. If I get it really really good it might be as fast as a modern 500

It's more about 'originality' to me.

Originality to how it came out of the factory, or how it was (ab)used when in service?

How my FiL had it....he bought it off a racer and tore around the countryside and various RAF bases on it

I've been speaking to Mrs. D about it, it's her bike after all. She has fond memories of her Dad having to literally jump on the kicker to get it going. She also asked me (unprompted) "Do they do classic bike trackdays?"

She wouldn't be the one kicking herself into a sweaty puddle when you stall at a set of lights.

Ah.


Have to admit that I'm currently pondering whether or not to investigate 'uprating' the engine in the JAPton back to 500cc or not.
It's currently a 402cc (350 bottom end with 500 top end IIRC) and there IS a pair of 500cc bottom ends in Dad's old spares pile (potentially going to be sold off unless I make my mind up to keep them). I have no idea if they're usable or not though (one is in pieces and only half there, the other is a complete bottom end, sans barrel).
However, I think there's a feeling from my brother that the bike should be kept 'as is', the way Dad left it. Bit of a quandry really (especially as there's a couple of other things I want to do to improve it), I see it as a continual work-in-progress, but the others see it as an heirloom.

Funnily enough - The JAPton was built up as a 'race-bike' and they did a few classic trackdays with it.

[JackyJoll]

I’d call an increase in capacity from 400 to 500 cc a useful improvement. It’s not like fitting 11:1 pistons.

[Mr. Dazzle]

OK, so after discussion with Mrs. D and her Uncle - who owned and ran this bike in the 80s - I've decided to take the utterly foolish step of fitting the 11:1s. Mostly 'cause that is what the bike always had and what her Dad ran it with for about 30 years. They both fondly remember the bike being a bitch to own and run and they think it should stay that way!

Fortunately for me, there are two petrol stations which sell proper fuel nearby. I've been looking into it, Shell V-power might contain Ethanol depending on the garage but it's always 99RON. Esso Synergy Supreme 99+ never does according to Esso and it's always at least 99RON. I'll get some ocatane booster too and buy a timing light...

I'll also have, for now at least, nice shiny clean combustion chambers.

If it all goes horriby wrong at least I'm also experienced in changing the pistons now too.

[KungFooBob]

You could build your own starting rollers

[Mr. Dazzle]

Given my ability to weld and whatnot thats more likely to end in disaster than a seized engine would

My wife's uncle dispatched on the bike in all weathers when it had 11:1s so it can't be THAT bad. They did have 5 star back then though....

[Mr. Dazzle]

Fitting high compression pistons does raise a few queries in my mind about the head though....referring back to the pics from before:



First off repairs to the valve seats mean they're cut much deeper than a standard bike (below), so the 11:1 pistons won't actually achieve 11:1, it'll be 10.something I'd guess.



Secondly that sharp corner where the seats overlap the plug holes doesn't look too friendly, wonder if I should do something about that.

[Lutin]

Those valves (in the refurbished head) look to be really deeply pocketed. Not sure what that'll do to the gas flow.

[Mr. Dazzle]

Those valves (in the refurbished head) look to be really deeply pocketed. Not sure what that'll do to the gas flow.

Me neither....the head was refurbished 'cause one of the valve guides broke, it fell into about 20 peices while the engine was running. You can't really see it here, but the seats got a bit chewed up! This is the 'before', so you can see how much has been taken out. At first glance it looks like loads and loads has been removed, but if you look closer under the black you can see it's not that much.



P.S.

This is what happens when a bike has no air filters and shit oil control due to shiny bores and worn rings.

[Le_Fromage_Grande]

11:1 you should be okay on Super Unleaded, my Z1170 is 10.8:1 and that's fine on Super Unleaded, but make sure there are no sharp edges in the combustion chamber as these can start detonation (I don't know how Suzuki get away with TSCC)

[Nidge]

I cant remember from the other thread, but have you looked into the bottom end at all? Particularly whether the sludge trap needs cleaning?

[Nidge]

I cant remember from the other thread, but have you looked into the bottom end at all? Particularly whether the sludge trap needs cleaning?

[Mr. Dazzle]

I've not really looked at the bottom end beyond grabbing the rods and trying to shuffle 'em up and down (I can't). Oh, and keeping an eye on oil pressure, which is nice and healthy.

I know the crank came out in the early 00s when my FiL rebuilt the engine completely. Since then it's probably only done a couple of thousand miles although the state of the bores and chambers would suggest otherwise.

[Supermofo]

Why would you need super on an 11:1 compression ratio? Is that an old engine thing?

My 690 has 12.6:1 and my car has 14:1