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36 Chief Y motor performance mods

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cane

Posts: 74

Joined: Sun Nov 28, 2004 1:01 am

Location: Laguna Beach

Post Wed May 02, 2007 6:52 pm

36 Chief Y motor performance mods

I'm planning my 36 Chief Y motor build. I'd like to be able to cruise at 80mph on a nice hot summer day, all day, while maintaining reliability and stock engine life. I would also prefer to keep the bike stock looking. How close can I get to these goals, and how can they be achieved? Thanks,
Chris
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Cotten

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Location: Central Illinois, USA

Post Wed May 02, 2007 7:30 pm

After you break it in, put a really tall sprocket on it.

...Cotten
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cane

Posts: 74

Joined: Sun Nov 28, 2004 1:01 am

Location: Laguna Beach

Post Wed May 02, 2007 8:15 pm

Really? That's it? Will the origional oil pump be capable for this kind of service? What tooth count would you recomend. I wonder what the handling and vibration is like on this bike at that speed.
Chris
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Cotten

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Location: Central Illinois, USA

Post Thu May 03, 2007 5:38 am

Chris!

I'm a believer in basic factory design, figuring that motors were built for dependability in the first place. A lot of 'hop-ups' intended for competition can shorten the fuse.

Time has marched on, of course, so now there are a lot of improvements in material and quality control on replacement parts. Since this is a discussion forum, others shall chime in here with options like rad cams, bonne lifts, stroker wheels, Carrillo rods, etc., etc....
By the time you implement all of the available improvements for Chiefs that are now on the market, it probably won't resemble a '36 Y motor anymore.

But no matter what you choose, you will still need a bodacious sprocket to achieve the performance you have asked for.
How big you can go depends a lot on your choice of chainguard, but a 26t isn't out of the question. (But break in the motor with a much smaller one, as lugging can be disastrous.)

As far as the oilpump, the problem with all of them is not getting oil to the motor, its getting it back out.

As far as handling, how big are your forearms?
(Thank gawd for Eisenhower and his Interstate system!)

I, myself, am a student of carbs. When it comes time to address your Schebler, I shall chime in again.

....Cotten
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Lyle

Posts: 25

Joined: Thu Aug 25, 2005 9:52 am

Location: Moorhead MN.

Post Thu May 03, 2007 7:51 pm

36 Chief Y motor performance mods

Ok, The oil pump is the least of your concerns. I have a 38 Chief with a hopped up 48 engine in it and a 36 tooth sprocket and it won't get close to 80 mph sustained. It'll go 80, but not sustained all day long. If I were you, I'd stroke the engine out and get a tall OD 4-speed transmission with a large sproket on it. But the problem with the tall OD trannys are they are taller in first gear too so you need to put a smaller sprocket on the bike to get the same "feel" of first gear as your original sproket. The best you'll do with a 36 tooth sprocket is 60 - 65 mph sustained with the stock 3 speed. The reason is Chiefs with their long stroke don't like high rpms and they redline at somewhere around 4000 rpm. That combined with their 3 speed transmission really puts them at a handicap for running sustained high speed.
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cane

Posts: 74

Joined: Sun Nov 28, 2004 1:01 am

Location: Laguna Beach

Post Thu May 03, 2007 10:54 pm

How much stroke do you think would increase torque with out significantly reducing engine life? If I increase the stroke will I need to feed it more mixture? Cotton, do you mean that a chief responds to steering input like a subruban with out power steering? I wonder how is oil retuned from the engine to the oil tank by the early pump? Thanks for the input Lyle.
Chris
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injunjack

Posts: 77

Joined: Thu Nov 21, 2002 1:01 am

Location: Espoo, Finland

Post Thu May 03, 2007 11:20 pm

Cane

A modern carb, Bonne cams and lifters, taller sprocket in gearbox, smaller in rear. My ride is like that and I can cruise 70 all day. (except that I have to have a gas stop every 120-150 kilometers)

Like Lyle said, OD gearbox is really the answer. I have one muonted, but haven't had chance to ride it yet, so I really cannot comment how is the feel of the first gear.

Jack
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Cotten

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Location: Central Illinois, USA

Post Fri May 04, 2007 6:52 am

Chris!

I know nothing of Suburbans; My forearm comment refers to how one's arms serve as a steering dampener. Some fatigue faster than others, and "all day" can seem like a very long time for many of us.

As you may have already guessed, achieving your goal may result in two things: an empty pocketbook, and a machine that isn't much of '36 Chief anymore. How far you take it is your personal decision.

Philosophically, I personally can accept any modification that is reversible. The fourspeed OverDrive tranny, if you can afford it, is the most sensible and effective "modification" available today.

....Cotten
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cane

Posts: 74

Joined: Sun Nov 28, 2004 1:01 am

Location: Laguna Beach

Post Sat May 05, 2007 12:33 am

I like the OD trans idea. For the same performance, how would you compare the cost benefits of an OD trans versus engine mods?
Chris
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panic

Post Sun May 06, 2007 10:15 am

For the same performance, how would you compare the cost benefits of an OD trans versus engine mods

???
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Cotten

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Post Sun May 06, 2007 8:17 pm

Chris!

If we address this from the economic point of view, the OD tranny has a distinct advantage of allowing you to preserve your original tranny on the shelf, which can only increase in value without any further investment into it.
Rebuilding it will cost significant cash without any performance benefit, and that investment will depreciate by the mile. And it won't take as many miles as you hope.

Motor building is by no means cheap either (!), and it leaves you with bits and pieces left over on the shelf. Going for the max means replacing just about everything but your castings. And sensibly your early cylinder and heads castings as well.

As I mentioned earlier, going for every bit of possible ponies also means a shorter lifespan.
The OD tranny softens the blows a bit, increasing its worth to you in the long run by preserving the motor.

From that perspective, you get much more for your buck spending on the tranny than the motor.
However your high expectations demand every bit of what a fully max'd motor can provide in addition to the OD tranny.

Its only money.

....Cotten
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panic

Post Sun May 06, 2007 9:25 pm

Let me phrase that as a statement rather than a question.
The OD transmission does the following for "performance":
Nothing at all.
The gear ratio RPM drops are stock, it's not close ratio.
All it does:
Reduce the RPM in high gear.
It does not increase power.
It does not increase top speed (beyond what would be possible with alternate gearing).
Is that valuable?
Yes, but it has no more to do with performance than a larger countershaft sprocket.
By the way: the engine will turn more slowly with an OD transmission for a given MPH than with the same gearing and a stock transmission, but will require about the same power. The reduction in pumping loss from lower RPM is balanced against the power loss through in-direct drive in OD.
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halvor

Posts: 173

Joined: Fri Jan 09, 2004 1:01 am

Location: Norway

Post Tue May 22, 2007 3:34 am

while not adding any horsepower.. you will probably find the OD transmission to extract some "performance" out of the existing engine.

Unless you live in a very flat place... the 26 is too big for a 74" engine..at least my opinion.
It worked ok in my hilly country... but it will need a 84" engine for fun :)

I find the low ratio OD and a 25tooth near perfect for my country (and the 84" engine). Shifting is easy, and you can really accellerate out of the curves...lot's of fun.. Seems like a much faster machine then..:)
I shift to 4th gear at 55-60mph for highway cruising..but the engine is flexible enough to do 45-50mph in 4th.
But I shift down to keep the engine running happy (and no lugging).

I found the rpm to be ok at 75-80mph with the low ratio OD.. but you should consider the high ratio version for 80mph constant.
The max speed limit is 62mph here.. and the first 3 gears see a lot of use. Even on some of the main roads over the mountains, first gear have to be used to get through some of the hairpin curves:)
I have killed lots of transmission gears.. even 2nd gear in the OD box (manufacturing problem I think, replaced on warranty).. I blame some of this on the 26 tooth I had on the original box. The 84" makes a lot of torque and the repro/ orginal gears was not up to the task.

Still, with the rpm drop I have had problems with "external" oiling.
The return pump seems to suck out the oil rapidly, but then loose the prime. This will cause the oil level in the crankcase to rise a bit... and some of this oil exits the breather line. I have the scraper installed.. and while it works fine when it works.. I think the 90degree oil line fitting has a too large ID, and is mounted to far to the right. I have now soldered in a smaller id tube into this fitting, and this now sucks oil from the bottom of the crankcase. The tube extends into the crankcase.. maybe 1-1 1/2 "
So far it looks like this tube have reduced the "lost prime" issue.. the return pump keeps on pumping(or squirting ) oil constantly.
Still, some oil mist exits the breather line.. but I have near solved this problem with a vertical tube and som trick plumbing.

Anyway... I need a season or so to check it out.. too much theory and not enough real-life testing..
1944 Indian Chief + sidecar
1939/40 Sport scout bobber,
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injunjack

Posts: 77

Joined: Thu Nov 21, 2002 1:01 am

Location: Espoo, Finland

Post Tue May 22, 2007 11:51 pm

Hi

I just arrived to work. It was my first ride with my new OD trans.

I have 24/36 sprockets and tall OD.
My first impressions are that I'm geared a bit too tall for tall OD. I have to ride more, and see if I have to gear a bit higher. But I'm sure that with this combo, I'll be able to cruise OVER 80mph all day.

Jack
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halvor

Posts: 173

Joined: Fri Jan 09, 2004 1:01 am

Location: Norway

Post Wed May 23, 2007 2:06 am

Cool!

sounds like a bit tall gearing, yes... at least if you are riding here in Norway:)

I run my low OD with a 25/40

I believe you can get the OD sprockets from 22 to 26 from the manufacturer.
But it looks like the sprockets are some kind of standard sprockets.

I have a 23 for the day I'm ready to put on the sidecar..


anyway.. I have converted to ducati now.. so now I have 6 gears to play with:) But really.. even 1st gear can put me in jail for speeding..
1944 Indian Chief + sidecar
1939/40 Sport scout bobber,

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