Topic: 900 Motor questions

[JLeather]

I'm shelving the turbo build for now, but I can't just dump a stocker into this bike.  Where's the fun in that?  Since I gotta build a solid bottom-end anyway for the future plans I may as well have some fun with the top end for now.  Here's the build plan.

Henry Abe 900 kit
Some kind of aftermarket rods (not aluminum, maybe cryoed stockers?, or perhaps I'll blow the money for Falicons)
Ported Head, big valves
Andrews A-grind cam
APE modified crank and tranny setup, +lightened rotor
New primary chains (probably from Ken)
Good clutch (Tommy?)
Dumping out an RC 4-1 megaphone

Now, I got a few Q's before I jump in and start gathering components.  First of all, anyone know if the HA900 kit is forged or cast?  I'm lookin to get a set of HA pistons/cylinders from RickyRacer, hence the choice of the HA kit.  I'd really like forged pistons.

Secondly, is the Andrews A cam too small for this?  As I add displacement it smoothes out lumpy cams.  In an 836 the A-grind is a cool, mildly-lopey cam.  In a 900 is it gonna be too small?

Thirdly, mostly a question for Jay or someone who's got their crank work, is a lightened rotor in addition to a lightened APE crank going to hurt my idle too much?  If I drop too much rotating mass I get an engine that bogs too easily and doesn't idle well.  I want to avoid that, and I'd sacrifice some revs for a more streetable idle.

Lastly is an induction question.  I want something that will feed this motor streetably.  I've heard the the 28mm Kawi carbs talked about favorably before, the ones with the large drain screw for jet changes.  Are they enough carb for this motor or am I gonna have to source a set of 29mm smoothies?  I'd prefer something more streetable (less finicky) than CR carbs.  It's gonna be a primarily street motor, but I don't wanna under-carb it and have it run outta steam at 7-8k.  What have you put these carbs on before and how do they perform?  What do I need to do to a set for a motor like this?

Thanks guys.

[Jerry Rxman Griffin aka MuthaF'er]

There are 2 different Henry Abe kits out there. The NOS kit I'm sitting on is cast. Jay makes a nice crank too!!

[JLeather]

Is there a way to tell 'em apart?

[Jerry Rxman Griffin aka MuthaF'er]

Member Axl has pictures on www.Satanicmechanic.de

The ones I have do not have the "full" skirt. Axl has it labeled Type B Slipper. The instructions came out pretty #$%*ty. I think he has them posted also.

[JLeather]

Is there really any problem going with a cast 900 setup instead of a Wiseco forged 836 setup?  That's the other direction I could lean since they are readily available.  I do love the thought of a bit more displacement though.  It's gonna be a street-bike, not a race bike (well, maybe an occasional light race).

Has anyone with an APE crank experienced more bogging at launch or idle issues?  I know you gain a good bit of revs, but I'm worried about losing out on the launch and town-manners, especially with a pretty heavy bike (chopper, not a cafe).

[Andoo]

Nobody knows were to get replacement rings for the Henry Abe 900cc kit. I'd love to know, because I have a drag engine with a set in it. I think the wisco pistons have higher compression than the Henry Abe pistons. Also the valve reliefs are shallower than the wisco pistons so you run into problems if you want to run a hotter cam.

If the APE crank is lighter (I assume it is) the engine would rev faster through the entire rpm range.
Is the stroke on their crank stock?

Forged is denser so I’d imagine it doesn’t expand as much so you could make the tolerances tighter.

[fuzzybutt]

forged expands more and that is why clearances are set larger. it's also why a forged piston motor may consume more oil and be noisier on startup.

[Big Jay]

forged expands more and that is why clearances are set larger. it's also why a forged piston motor may consume more oil and be noisier on startup.

The modern forged pistons made from 4032 material run tight. We do Wiseco 836s as tight as .0015".

Jay

[Big Jay]

We no longer lighten the rotors. The early rotors had a huge flange on them and were very heavy. The later ones were lighter, so everyone went with them.

Haven't heard of any one having bogging issues with our lightened cranks.

Every ABE piston kit I have ever seen was cast.

Jay

[MRieck]

forged expands more and that is why clearances are set larger. it's also why a forged piston motor may consume more oil and be noisier on startup.

The modern forged pistons made from 4032 material run tight. We do Wiseco 836s as tight as .0015".

Jay

Interesting...I do .017. The ring gap on those pistons would want you to run .012.

[MRieck]

We no longer lighten the rotors. The early rotors had a bug flange on them and were very heavy. Ne later ones were lighter, so everyone went with them.

Haven't heard of any one having bogging issues with our lightened cranks.

Every ABE piston kit I have ever seen was cast.

Jay

Jay's cranks work OK. I can have the later rotor balanced for you....I have a balnced crank to attach it too. I can also have the clutch basket balanced.

[fuzzybutt]

forged expands more and that is why clearances are set larger. it's also why a forged piston motor may consume more oil and be noisier on startup.

The modern forged pistons made from 4032 material run tight. We do Wiseco 836s as tight as .0015".

Jay

wow thats cool, 15, 20 years ago when i was building motors for fisher buggies we were setting clearances about 2x that with forged pistons.

[Bodi]

Every production sport bike uses cast pistons - and they get some serious horsepower from them at insane RPM. Why is there this mystique about forged pistons? The basic advantage is that they're cheaper to make in small quantities. Cast pistons - when designed and produced properly - are far superior. If Yamaha thought forged pistons offered better performance than cast, you would find forged pistons in an R1 engine... nope, cast pistons. Same with Honda, Kawasaki, Suzuki, Triumph, Ducati... maybe a Ural has forged pistons?
Yes, cast pistons cost a bit less in production volumes - you pay a lot up front for the tooling.
Modern Cosworth process casting can have different alloys at different parts of one piston and optimize metallurgy for different needs - this is impossible with forging. Forged piston metal has to be ductile enough to flow well at plastic temperatures, limiting the metallurgy choices.
Realistically, I suppose aftermarket cast pistons have a probably-deserved poor reputation. If I am designing a Hayabusa engine, I have a good size production run planned and the pistons will be absolutely optimized for my engine, and made by a huge piston casting facility with the latest machinery. An aftermarket casting will likely have to accomodate a variety of bore sizes and valve cutouts (making the mold tooling would be prohibitively expensive for a one-model piston), with the necessary metal thickness for them. They're not likely to have the latest high-tech casting systems either.
So, whatever works for you, I guess. If there was a stock modern sportbike cast piston that would fit in an SOHC-4 engine though... that would be interesting.

[754]

There is a few good reasons for running forged pistons, like less chance of burning thru, greater strength, ability to run thinner section...none of which matter on stock engines.

It depends a bit on what you want to do with it, and wether you can mod pistons yourself and other factors.

[Jerry Rxman Griffin aka MuthaF'er]

Nobody knows were to get replacement rings for the Henry Abe 900cc kit. 

My NOS Henry Abe kit has 1 piece oil rings still in their boxes. The same thing will happen to those pistons that just happened to my NOS 1080 73.75mm pistons. I will send them to Total Seal. If Total Seal can match them up that's great. If they can't match them up I will have them cut the pistons for 3 piece oil rings as they did for the 1080. When this happens, which will not be too soon, I will have a full set of stock Henry Abe rings available PLUS all the info necessary to convert to 3 piece oil rings. I plan on picking up the 1080 piston kit and rings this week and then I'll be able to let you know what this cost me.

[Big Jay]

Some of the oem Japanese bikes had forged pistons. I believe the GS1150 was one. Forged pistons are way stringer than cast. The only reason the oems use cast pistons is weight. A forged piston is made with a punch that looks line the inside of the piston. It has it's limitations as to the shape it can punch. With a casting, for instance, you can have material removed above the pin boss as cast. With a forging, it would require internal machining to do this. The weight issue is the only reson oems use cast.

Jay

[Terry in Australia]

I always thought forged pistons were stronger, (hence their popularity in blown drag car engines) but cast pistons were more common, because they were cheaper to make? 

[JLeather]

Terry, forged pistons are used in all forced induction applications and anything you're gonna be spraying with NOS.  Forged pistons take heat better, whereas cast will crack or melt holes.  For a stockish bike (the motor I'm planning) cast is probably ok, but I'll have to watch the heat.  An oil cooler, etc.

Forged pistons also fail *gently* in many instances.  Where a cast piston cracks into pieces, and punches these pieces out through your head, forged pistons fail more ductily (sp?) and kinda give you a warning so you can shut it down before they ruin other stuff.  All in all, though, you guys are right.  Cast is probably ok.

I am a bit surprised that no one has noticed more bogging after a lightened crank/rotor combo.  I suppose it may be because the bikes didn't have that much torque to begin with?

[754]

I think where you would notice it is idling through town in higher gears at lower speeds, pulling a trailer or sidecar.

Most of which, no one that hops up their to the point they will put another 250$ into the crank, spends a lot of time doing. They are usually revheads, a lot on here say they dont see much morepower till above 6 or 8K.

That alone makes me a bit reluctant to do it, along with porting for maximum flow, it just seems that I would loose a lot in the middle where I spend most of my time. That and I can always pull off the Alternator for the drags.

I run the smaller rotor that has still been lightened. I cant see the need to balance an uncut one they were done at the factory.

[JLeather]

I envision a portedhead that's more for intake charge velocity than max flow.  Ported for smooth transitions, but running stock-sized valves.  With the 900 bore it unshrouds the outside edges of the valves which further improves flow.  Higher intake charge velocity actually improves torque.  If I combine that with a moderate cam and an extra point and a half of compression I should actually see a lot of gain in the middle.  That's why I'm trying to figure out if I want to lighten the crank, and if so how much.  Being that this is a street bike I see myself spending most of my time between 4500-7500.

Is the stock crank balanced well enough?  Do you only rebalance after lightening, or could it benefit from a more precise balancing without a lightening?  Would I be better off just lightening the rotor and keeping the crank stock, or perhaps better off lightening the crank and keeping the rotor stock?

[Andoo]

Nobody knows were to get replacement rings for the Henry Abe 900cc kit. 

My NOS Henry Abe kit has 1 piece oil rings still in their boxes. The same thing will happen to those pistons that just happened to my NOS 1080 73.75mm pistons. I will send them to Total Seal. If Total Seal can match them up that's great. If they can't match them up I will have them cut the pistons for 3 piece oil rings as they did for the 1080. When this happens, which will not be too soon, I will have a full set of stock Henry Abe rings available PLUS all the info necessary to convert to 3 piece oil rings. I plan on picking up the 1080 piston kit and rings this week and then I'll be able to let you know what this cost me.

Thanks a million, cant wait to hear results.

[JLeather]

The Wiseco 836 pistons are already 3-piece oil rings right?

[MRieck]

.

I cant see the need to balance an uncut one they were done at the factory.

I've had several later uncut rotors balanced. Both were off. Same goes with cranks. Clutch baskets too.

[754]

You said you are balacing on a crank.. which make sense if that is the crank it will be run with. .

To balance rotor by itself should it notbe on an arbor, if you are trying to balance it only??

[MRieck]

You said you are balacing on a crank.. which make sense if that is the crank it will be run with. .

To balance rotor by itself should it notbe on an arbor, if you are trying to balance it only??

according to my balance guy (and if I remember correctly) it is a wierd size/taper. It was easier to balance a crank and then mount the rotor. The good thing is the crank can, and has been, used again to do rotors. The clutch basket gets mounted on an arbor OK. the nice thing about balancing the basket it gets rid of the up/down inbalance as well as the wobble inbalance