[Warwick]

I am about to begin a 535 upgrade on my bullet as its done over 20,000 kms in standard trim. I am getting the alloy barrel, forged piston, roller bearing, etc. This is the second bike, I have done it to (with the much required assistance of a mate). The first one I went the whole hog with ported head, big valves, etc etc. Great result with increased performance. The only negative is some piston slap and the engine feels way less refined as you really feel each combustion bang. After a 2 years riding all mud guard stays and indicator fittings have broken.  I am not complaining as thats what I expected and its fun. In an attempt to tone it down a bit and be a bit cheaper, I am keeping standard valves, oil pumps, rockers (depending on wear and condition) and minor porting.  Any thoughts or advice?
Cheers and beers
Warwick 

[ace.cafe]

Make sure the piston/pin weighs less than 500 grams, and the crank runout is less than .002" overall on the stub shaft ends. Preferably less than .001" runout, if you can get it.

The only physical reasons for the engine to have increased vibrations from the 535 compared to the 500 would be too much piston weight, or the crank runout was more on the rebuild.
It is possible for a 535 to be smooth as silk, considering a single.

Aim for 135 psi cranking compression test result. Generally speaking, if you use the 8.5:1 forged piston, you will need to rephase your stock intake cam 1-tooth retarded(anti-clockwise) to get that test figure without using compression spacers under the barrel.

Do those things, and you should be a happy camper.

Oh, and if it has the later style oil tank engine breather, restore it to the original crankcase side breather when the engine is apart.

[AzCal Retred]

Warwick - was this just the Alpha bearing in the stock potmetal rod, or Alpha in a new steel rod, or a complete Hitchcocks crank? The crank is the key to making power. Without it, every "throttling up" ride's a crap shoot on the hinky stock bottom end and potmetal con rod. Next in line is a forged piston to take some pounding, otherwise the stock soft alloy unit frags & takes out the cases. Then there's the matter of obtaining an alloy cylinder, unless you just ride in the winter.

As best I can tell, there's no way to get a steel rod, roller bearing big end, properly balanced crank assembly, and forged piston in alloy barrel for less than about $2K even doing most of the work yourself. As Ace has pointed out many times, without these items you're up the creek, power-wise. The best option I know of is to get the Hitchcocks new flywheels (FLYWHEEL SET FOR STEEL RODS, UK MADE
Part No: 90128A , £399 / $520), and the steel con rod with fitted roller bearing (CON ROD WITH FITTED ROLLER BIGEND (RE13), FORGED STEEL ; Part No: 90125A ; £495 / $650). These are about £900 / $1170, and you could assemble them yourself but you'd still need some presswork to transfer the shafts over from the old crank. But for only another £150 / $200 you can get an already built crank (CRANKSHAFT, LONG STROKE, INDIAN 500cc, Part No: 200160A ; PART No. 200160 ; PERFORMANCE CRANKSHAFT, 500cc INDIAN MODELS) ; £1,050.00 / $1370). You'd have to find someone that would supply a good alloy or steel con rod and roller big end bearing, then tear down & reassemble & rebalance your old crank for $1500 just to break even. Even $1600 would be a smoking good deal, as presswork isn't free or without risk.

I'm thinking that if you got the 500cc 9/1 piston ( PART No. 42877/40 ; PISTON, 84mm +40, 9:1, C/W RINGS ; £88 / $120) and the 2mm compression plate (PART No. 200480 ; COMPRESSION PLATE 2mm ; £12 / $16) you would just be out a bore job on the existing cylinder & some gaskets. With the plate you should end up around 8/1 CR, a useful increase over stock, OK even with an iron cylinder. Then just ride it reasonably until you get the $2K socked away to allow you to play in the lofty 30 - 35 BHP stratosphere. Ace's intake retard strategy will allow it to spin a bit more and reduce kickover resistance. The better piston will survive the slightly higher RPM way better, and the stock oiling system will have plenty of volume when running freely instead of lugging.

As my old drag boat buddy Vince told me years ago - "Speed costs money - How fast can you afford to go?" Without the whole balanced crank/steel rod/roller bearing/forged piston/alloy cylinder package, pushing the Bullet motor hard just starts the fuse burning.
 

[ace.cafe]

Just a note to the above, I think the regular stroke is the better crank option, not the long stroke.

[Adrian II]

Bullet Whisperer uses these high comp pistons quite a lot, though he reckons true compression on these is nearer 7.9:1. There's one in my Not a Fury/ASBO14, but he modified the cylinder head combustion chamber and piston crown to get a decent squish band, I think he said it's running at 8.3:1, cam timing still on the dots for the moment.

+1 to the steel con-rod to go with that roller big end bearing, and also to retarding the inlet cam one tooth if you ARE getting bad vibration problems with a higher compression engine. My other ASBO Bullet, ASBO 12 was taken up to 10:1 on its AVL/Electra-X top end, with a real vibration problem in its wake, it snapped two head steady straps and a silencer/muffler bracket. On B.W.s advice I retarded the inlet cam by one tooth and it made the bike much nicer to ride with no apparent loss of performance or snapped things since.

A.

[cyrusb]

Adrian, so what you are saying is higher compression caused that destructive vibration, not an out of balance condition? And when you reduced the compression you had no reduction of power but a reduction of vibration. Sounds too good to be true. A balanced engine will be balanced regardless of its compression ratio. And an engines power level will drop with its compression ratio. So how does this add up?

[AzCal Retred]

Adrian or BW - Any idea where these high silicon 9:1 CR pistons are sourced from? Hitchcocks seems to be letting their stock of them run out as the standard & 0.020 over ones are gone. A good piston & rings for $120  vs. $200 is a frugal way to upgrade. Having a stock piston stick in the bore & pull apart isn't my idea of a way to spend a sunny afternoon. A good low-expansion piston even at 7:1 or 7.5:1 would be a real asset.

[Adrian II]

With the high compression modifications still in place I just retarded the cam one tooth following advice, I did not revert to stock 500 AVL or Electra-X barrel and piston, which is already on 8.5:1, compared to the iron barrel Bullet's 6.5:1!

The crank in ASBO 10 was originally one of the original Electra-X cranks with one of THAT BATCH of crank pins that would fail after about 15-17000 miles. It was taken out of someone else's Electra* and after sitting around for a while, it was rebuilt with an Alpha Bearings sleeved con-rod and UK-made crank-pin by Henry Price (whom I also trust to build a crank properly). Along with a stock Electra-X piston there was nothing to upset the stock crank balance, i.e. steel replaced steel. B.W. tuned the engine to ASBO spec a few years later, but the amount of metal taken off the piston would not be enough to upset the balance.


AzCal,

The Hitchcocks' 9:1 (claimed) pistons actually came from the USA in the first place, according to their catalog. Their forged 8.5:1 pistons were made by Accralite or Omega in the UK. Henry Price also has 500 and 535 iron barrel pistons with a higher comp than stock, though I think they're still only 7.5:1, might be worth checking out.

https://www.pricepartmotorcycles.co.uk/ourshop/cat_314448-Cylinder-Pistons.html

A.

* The original Electra-X my crank came from was rebuilt with another crankshaft under warranty.

[AzCal Retred]

Thanks for the PricePart link, Adrian - 7.5:1 is probably a good place to stop on a stock bottom end I think. - ACR -

[ace.cafe]

Adrian, so what you are saying is higher compression caused that destructive vibration, not an out of balance condition? And when you reduced the compression you had no reduction of power but a reduction of vibration. Sounds too good to be true. A balanced engine will be balanced regardless of its compression ratio. And an engines power level will drop with its compression ratio. So how does this add up?

Cyrus,
Once the compression gets high enough that the fuel cannot sustain regular burning, it goes into detonation, and the ignition timing is no longer in control.
When this happens, especially in the case of early pre-ignition, the burn cycle becomes jerky and irregular, causing, vibration, loss of power, and also likely causing damage.
So it is a remedy to bring the compression down to a level that the fuel can withstand, and the the damage can be avoided, and give more power because all the timing events and burn cycle are under control.
In the Bullet, the compression limit is about 155-160psi on a cold cranking compression test with premium grade fuel.. It is very common to exceed that with a high compression piston and keeping stock cam valve timing.
We always ran rephased stock cams with our pistons, and we used basically that same timing with our Magnum cams. It keeps the engine working within the pump fuel limits.

If running methanol or race gas with real high octane, then compression can be raised to take advantage of those fuels.

[ace.cafe]

Adrian or BW - Any idea where these high silicon 9:1 CR pistons are sourced from? Hitchcocks seems to be letting their stock of them run out as the standard & 0.020 over ones are gone. A good piston & rings for $120  vs. $200 is a frugal way to upgrade. Having a stock piston stick in the bore & pull apart isn't my idea of a way to spend a sunny afternoon. A good low-expansion piston even at 7:1 or 7.5:1 would be a real asset.

They are Robbins pistons.

[cyrusb]

Ace, got that. But detonation and knocking was not mentioned in the post. I would think that if it was that violent it might have been mentioned.

[AzCal Retred]

Ace - Robbins was a new name for me. Looks like they are gone, maybe ten years now? Just NOS remains.

Cyrus - Honda went GP racing in the 60's, discovered with their 50cc Twin that detonation issues became a non-issue after 22,500 RPM...! They had to run the cheapest regular that they could find to so the flame front would keep up with the piston speed. There are a lot of complex interactions happening inside the infernal combustion engine, a lot of which were discovered by the "cut 'n try" method. Boat propeller design has a mechanical balance component and a hydrodynamic one as well. Lots of props & bearings were sacrificed to vibration before early racers stumbled onto winning combinations of pitch & curve. Whatever works is valid, sometimes the explanation takes awhile and a lot of pricey R&D time. Look at Burt Munro (https://en.wikipedia.org/wiki/Burt_Munro) and his 200 MPH Bonneville effort - all on a shoestring and seat of the pants tuning. Vibration can have multiple causes and some stunningly complex interactions.

[ace.cafe]

Ace, got that. But detonation and knocking was not mentioned in the post. I would think that if it was that violent it might have been mentioned.

Right, it wasn't specifically mentioned, but I knew from the description and parts combo that it was over the limit.

[cyrusb]

Ace - Robbins was a new name for me. Looks like they are gone, maybe ten years now? Just NOS remains.

Cyrus - Honda went GP racing in the 60's, discovered with their 50cc Twin that detonation issues became a non-issue after 22,500 RPM...! They had to run the cheapest regular that they could find to so the flame front would keep up with the piston speed. There are a lot of complex interactions happening inside the infernal combustion engine, a lot of which were discovered by the "cut 'n try" method. Boat propeller design has a mechanical balance component and a hydrodynamic one as well. Lots of props & bearings were sacrificed to vibration before early racers stumbled onto winning combinations of pitch & curve. Whatever works is valid, sometimes the explanation takes awhile and a lot of pricey R&D time. Look at Burt Munro (https://en.wikipedia.org/wiki/Burt_Munro) and his 200 MPH Bonneville effort - all on a shoestring and seat of the pants tuning. Vibration can have multiple causes and some stunningly complex interactions.

Been in the business since 1973, very much aware of the problems of harmonic interference. However, detonation and knocking were not mentioned in the above entry from Adrian(this is the second time I am revealing this). These forces evidently were violent enough to break 2 head stays. I would think that would at least merit a mention of knock. The post suggests the destructive vibrations come from too much compression, as lessening it smoothed it out. Anyone who has run too much timing/compression to the point of knock knows its noise is the most prominent indicator, rather than broken engine mounts. I believe engine smoothness is controlled by the rotating mass balance and not engine output.