470 Pro-circuit

Crank works in Arizona can do it. Some times they can match an existing rod up with shorter length.

No worries cause they weld up old hole and bore another one.

Then when all said and done, they balance the crank.

You may also have to machine crank webs a touch or top where liner stops.

Was going to do it on newer Husky then use a 97 Rm 125 rod.

Kartwheel correct, on the shrinked rods. They do that on thumpers a lot.

If it was me! Pick up the phone and call Mitch. He could prob tell you everything they had to do and prob might do one for you?

Couple of thoughts-Does anyone know where to find the connecting rod c to c length of some of the best running Open Class vintage bikes?
430 Husky,440 Maico,490 Maico,465+490 YZ's,etc? Would be interesting to see how they compare.

Also,shortening the connecting rod has a significant effect on power delivery.A shorter rod with the same or longer stroke increases the "hit",
but might narrow the powerband.Example is putting a 6" or 6.125" rod in a small-block Chevy in place of the 5.7" standard rod.The longer rods increase the pistons dwell time at TDC,
making for a broader power curve.Another effect of the shorter rod is that the thrust angle is more severe,and 430 Huskys already have some issues with cracking cylinders,etc.

Just thinking aloud.

Pro Circuit has no interested in helping with these old Husky's. I already asked.

I've tried to contact pro-circuit about their 500 TC. But no answer .
Writing and reading English language is one thing, but phoning and talking
is another. Especially if you want to talk to the big boss.
Must pass all the secretary walls.

Motocross action june 82 (when I find one) will give more détails, I expect.

We have to remember that at this time Pro Circuit was not the powerhouse company and team they are now, they were a tiny shop which was really Mitch doing all the engine work and Bones doing suspension. Those are the only two guys who would know anything about the Husky era of PC stuff.

love how the bikes on a flat stand with a rock jammed under it..

the problem is the stand has Honda on it so not specific to this exact machine

the rod length issue is correct, engines respond to input
all the newer 4 strokes have the wrist pin at the oil ring
a couple of reasons you example of dwell time is correct for combustion events, but there is a whole science behind that
these are 2 strokes and i see the majority still carry a long skirt for piston stability in a windowed bore

another topic about this
port timing is important and yes you could raise the cylinder to adjust but you need to compensate for filling and scavenging the cylinder, 2 strokes also matter on case area for transfer, if you increase the stroke you will need more air, my 430 and 500 share a bore but the 500 has a different looking crank, Husky might have considered that
there are books and computer models for flow characteristics that can be had to help understand flow and how to best manage it, the management is the big deal, 10 years ago 300 horsepower was worth talking about, now grocery getters have that
the new 300 Husky has an amazing amount of BROAD power, so they learned to manage the flow to get the power
how do you take advantage of a stroke, typically bottom power, so for balance you would open the port timing for top end power, where is the balance, first you need to know what you want the engine to excel at

just rambling

I guess the point I was trying to make is that when you are working with a finite parts supply,
such as a 30 some-odd year old dirt bike needs,you have to balance the need for speed with the need to be able to ride PERIOD.

I have seen way too many race motors at the local level grenade needlessly.
Wise man says,"You can't win if you don't finish".
My father always said,"Be quick,but don't hurry".

Thinking aloud again(lol).

most of the problem is the same problem 2 strokes have always had...lack of knowledge/maintenance. an oe or oe quality rod in a swede lasts a loooong time....hundreds of hours. a properly rebuilt topend runs well over 100 hours and going over 200 is not rare at all, the bike just needs clean air and decent jetting. backing the timing off some helps with kickbacks and engine life no doubt.
im all for modifying things but after a pipe, port cleanup, and proper jetting a 430 really rips and it does it over the entire rpm range. the 500 is the same way with less rpm and more torque. why someone would go into extensive deep mods on the 430 is beyond me.

You would be amazed on what just a couple things can do to the standard 430. Adding the Mossbarger reed cage ( which was sold by Husky products ) and the Geoff Morris pipe
just plain enhances all the power range and give a real nice upper mid range kick. Reeds are easy to get and I usually have a couple extras here.

I was going to go ahead and add the porting mods from husky newsletters on my 430 cylinders , but Rick Horvart says it is not easy on piston and ring life. So no need to add.


But I all encourage anyone to have some fun and reproduce a classic project like the pro circuit bike. Would I make my everyday riding bike maybe not, but the project could be fun.

But if anyone does this project - please do a nice long you tube. Would like to hear that
exhaust !

Its actually an TE/TX frame with the center bar under the cases so the bike wont sit on a flat top stand without falling off unless you put something under it.

all of mine are that way

You have a TC with the rear frame loop and the bar under the engine? I dont know much about the four strokes, but I know the first four stroke built for Micky Dymond was built out of a TE because they didnt have any TCs yet.

no, all of my swedes have a center frame bar lower than the outer ones. even my 79 wr250 was that way. i thought only the motocross models would sit on a flat surface.

The two stroke CRs did not have the center bar, at least up to '84, maybe after than they all had it. The four stroke in that picture I know for sure is not a CR/TC, it was built out of a TE.

Thanks to ken44yz for providing the scan of Motocross action of june 82.

Thanks for this thread. I am in the process of building an '81 430 XC. To make a long story short, I have come to realize that it has a 470cc PC kit. My ace mechanic nephew and I realized it was a stroked crank as we were installing the new piston. We measured the stroke to be about 81mm. It is really interesting what you sometimes find in as you are rebuilding a bike from a collection of parts.

You are the messiah
This thread is 6 years old, but we still haven't the correct specifications for this 470 PC KIT.
All datas are welcome by a lot members of this forum:
Bore x stroke.
Cylinder porting.
Carb specification.
Exhaust.
Spacer under cylinder.
Head cylinder work.
Rod lenght, etc...

Of course all pics are welcome !

yeah, measuring the timing and size of the portwork would be great