88ss Exhaust Design

t ingermanson said:
I believe you're right. There are a few racers/builders who have utilized the PW3 that I've spoken to, and they've all reported an increase in power in the top end with some fiddling with timing as John has mentioned in a previous post, with a lot of fiddling with exhaust and intake to fill that hole in the middle you mention, and/or a 5 or 6 speed.

That cam in the 500 only sounds good, because that motor does rev much more freely, particularly with the lighter piston/long rods. It could be pretty fun to build and run the small motor instead of thinking I can build a big cc hotrod and not get into too much trouble. The roads here are tiny and twisty, or way over capacity, so a big hotrod can't really be used to it's full potential.

I've already got a good SS cam that I'll probably use in the motor to play it safe with the relatively fragile 88ss crank. When I started this project, there were fewer time and money constraints than there are now, so less fiddling and more riding sounds better and better.
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You could always try to obtain a one piece Landsdown crankshaft for your 88, yes they do exist, a friend of mine has one but bike is unbuilt state.
 
Bernhard said:
You could always try to obtain a one piece Landsdown crankshaft for your 88, yes they do exist, a friend of mine has one but bike is unbuilt state.
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I've got a NOS 88ss crank I'll be using. I'm not racing, so for my purposes I reckon it'll be just fine.
 
Sorry this post is a year late. I hope someone finds it useful.

The stock 88 is a very strong engine, unlike the 99, and for fast road use does not need any 'improvements' in this area.

I did race a 1959 Domi 88 in the late 70's and early 80's ( during that period mine was the only one still being raced in the southern half of England). Apart from breaking a cam follower , the motor was completely reliable and thrashed up to 7300 rpm with a dynamo crankshaft, 9.0 ish:1( I never measured it) pistons, 30mm Concentrics and 650SS head ( after 2 years with a standard head). Cams I tried were the stock daytona, 650SS and Commando 4S (and yes, the Commando timing cover with cam driven points does fit straight on the old Domi crankcases) . Exhaust pipes were 1 3/8 " with long megaphones, then Dunstall Decibels and finally a home made copy of the Norton 750 Formula Racer 2 into 1 with short megaphone. The twin pipes / long megaphones sounded the nicest, especially on the over run!, the Decibels and the 2 into 1 gave a wider spread of power but I settled on the 2 into 1 because it was light and tucked neatly out of the way. (My ID picture shows the bike in it's early form with Triumph high level pipes). In it's penultimate state (with 650SS cam) it was the fastest 500 twin 4stroke on the track at Club level and that included the latest Italians, which seemed to run on pony power rather than horse power. Most Commandos were also passed with ease. With the 4S cam acceleration above 90mph was quite staggering, but odd vibration at the carbs caused fuel starvation problems I hadn't fixed by the time I retired.

It was, however, unsuitable for road use as the power was all above 4500 rpm. For road use I would sleeve the SS head inlet ports to 1", fit the 650SS cam, 1 1/16" or 28mm twin carbs, high comp lightweight pistons (not heavy Indian types) and use the 2 into 1 exhaust (1 3/8" pipes).

Make the bike as light as possible. standard wheels, brakes and front forks are very heavy. Mine weighed 300 lb including fairing, fuel and oil. I could lift it off the ground by myself! A very stable bike at any speed and direction, but required a sharp application of opposite lock to force a rapid change of direction.

Doug Hele used very large bore exhaust pipes on the Domiracer and when I queried it with him he said that the lower overall exhaust back pressure gave better performance than the stronger pressure pulses from smaller pipes.
 
Not forgetting he ran 8.000 od , on the I.o.m. 500 Domi .

If youre after unihibeted high r.p.m. output , you dont ' tune ' the exhaust as you would a rally car system , for mid range .

That was where the ' 3 S ' P R Cam was supposed to be the Daytona High rpm output device - aiming for Max Output for SPEED .

Using the Boyer Spec. 1 3/4 pipes on a Triumph , you can pick up 1.000 rpm , over non tuned lengths .

Theres a theory , more applicable to High R.P.m.s regarding wall drag and stagnent gas speed on the walls - therefore to I. D.
is not the full operating area of the pulses . They require a ' correct ' cushion distance to wall for least drag / maximum velocity.

UP AROUND 8.000 odd . The works 500s ran 99 size journals . Obviously for strength & ridgidity for the high rpm , likewise the ecentriv valve gear Adj.
 
Matt Spencer said:
UP AROUND 8.000 odd . The works 500s ran 99 size journals . Obviously for strength & ridgidity for the high rpm , likewise the ecentriv valve gear Adj.
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The 500 Domiracer used the 650 big end size , the 99 was the same dia. as the 88 which is why the longer stroke 99 is a weaker engine.
 
Matt Spencer said:
willa Triumph Crank goinit . ? 82 stroke matches 99 .
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No. It's a 500cc motor. I've got an 88ss NOS crank that's going in it.

Now it's just a matter of which barrels to use. I've got a pair that's been bored for a +.040", but someone overshot the bore size by .004". Thinking of getting them nikasil plated, and using a pair of old pistons I've already got. Good pistons for the 88ss (9.5:1-ish) are harder to come by than the barrels. Plenty of heavy 7.5:1s out there, or the JS pistons and rods, but there's a budget I'm trying to work under, and the upgrade can of worms has no bottom.
 
A C - 15 ( BSA ) piston's 67 , wonder if . But seems they wanna sting ya .

88ss Exhaust Design
 
Matt Spencer said:
A C - 15 ( BSA ) piston's 67 , wonder if . But seems they wanna sting ya .
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88 GPM pistons are available, but are much heavier than original. I have a set of original pistons in the +.040" size, so it's a matter of bringing the bores back to the correct clearance. BoreTec's phone has been disconnected, who's been a popular choice for cylinder repair and plating.
 
Spoke to Millennium Technologies who do a lot of Nikasil plating. The fellow on the phone said plating a cast iron cylinder or liner is a 50/50 success rate, with bubbling up of the plating being the negative result. I'm sure he was couching, but it was an effective couch. Cost is about $1000.

He recommended an aluminum liner, then Nikasil plating. Cost is about $1400, for a more assured result.

Hard to justify at that price. I'd rather put that money toward a light piston/short rod kit.

I've got another 88 barrel at a worn +.020", so looks like those are the winning move for a +.040" overbore.
 
They used to throw Cortina ( 1300 / 1500 ) pistons in the Commando 850s , with sleeves for the bigger ones .
Bloke used a Fiat piston & Rod , in a 500 T single .

Some old dump with lots of pistons might dig out a set , but if its out of a four , you might need them both for 10 quid . perhaps .
 
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