1986 510 4stroke twin shock project phase #2

[ruwfo]

OK Guys,

It's a New Year & time for my 510 4stroke twin shock project bike to go to the next step.
here's a link to the original thread:
http://www.cafehusky.com/threads/1986-husky-510-4-stroke-project-bike.6708/

As you may remember last year, after 2 years of ownership, i finally got my $100 junk
back in working order. Rebuilt engine, new graphics/reworked body work, many hours of work
& mics parts . But as i said last season, i still wanted to have a 510 twin shocked bike for
my Vintage MX racing. So after some research & plenty of help from this forum, i think i'm
ready to go to phase #2.

What i'll try to do is show how i'll get there. I don't have easy access to a welder, nor do
i know how to, so i want this to be a mix & match parts project with a limited fabrication
( i hope). I also don't want to ruin any thing on the original 510 , so i can put it back to
stock should i or anyone else wants to .

What i'm starting with is a 1986 510 4 stroke, 1981 250CR rolling chassis , 1983 430WR frame,
swingarm & airbox, + a bunch of different year/model swingarms, shocks, 1984 510 exhaust &
tons of misc parts.

I started out thinking i'd just drop the motor into the 81 250CR frame, but found out the carb
come very close to the "V" in the frame where the front of the airbox would mount & the motor
mount holes are slighty off & don't line up. I also wanted to retain the dual exhaust set up, so
the original 510 air box won't work as it mounts to right side of the bike & would be in the way
of the right pipe.

So i partly switched gears & located a 1983 430WR frame, which should allow more room for a
air box behind the carb, the normal location for the twin shock 83-85 510's then the 81 frame
would.

As i'll be mixing & match Husky parts from different years, i'll try to show what's what from
year to year. I'm sure it will be a good education for all us Vintage Husky guys.

Husky John

 

[ruwfo]

As I said in my 1st post, i had a 1981 250CR rolling chassis, which i though i could just drop my 86 510
motor into. Well the motor fit's sort of, the carb comes close to the front air box mount & there no room
for the 510 air box which mounts on the right side & the front motor mounts don't line up completely

I want to retain the dual exhaust, so the 510 original air box had to go. I was willing to modify the front
motor mount, but still thought there maybe a easy way.

Husky John

 

[ruwfo]

So after doing some research & talking to guys here, i though a 1983 or 84 2 stroke would better suit what i wanted to do.

Here some comparison pictures of the 81 250CR & original 86 frames front mounting tubes

 

[ruwfo]

Here some comparison pictures of the 83 430WR frames front mounting tubes & the difference in the 81 -88 front
motor mount plates. I went with a WR frame because it had the same coil mounting bracket as the 510 has,
so it will be a straight bolt. More to come

Husky John

 

[Michel Dufayard]

510 motor from Uwe Picasso ( Germany) in a 80-82 frame.

 

[Michel Dufayard]

510 of Thierry Laloge ( france). A alloy airbox in a 82 frame !

 

[LEADVILLEHUSKY]

YOU SHOULD TALK TO OLDHUSKY CHUCK! HE DID ONE OF THOSE A FEW YEARS BACK VERY FAST!

 

[oldhuskychuck]

this one???i had to modify the frame, and make some special bushings for the swingarm...but it was a stupid fast bike.

 

[ruwfo]

Your Bike (oldhuskychuck) & some of the links Michel posted before were what i was using as a guide. But i want to keep the Dual pipe exhaust, so i need to go a slightly different route then Chuck. I should have the motor out of the original frame in a day or so.

I saw that the swingarm pivot bolt was smaller in diameter then the single shock ones are, so yes, i'll need a spacer/bushings to make up that dia difference.

I'm also thinking of going with a different shock/swingarm then stock as well, as i have aluminum one i bought a few years back from a 1980 CR.

But 1st things 1st
Husky John

 

[Michel Dufayard]

Ruwfo
Could you please post a picture of your aluminium swingarm, just to see.
Thanks

 

[ruwfo]

Well here's some pictures of the motor mounted. As you can see in the 1981 frame the motor mounts don't line up right. And without the frame cutaway the carb won't fit.

The motor does fit in the 83 frame ( i tried again last night ) but the frame bracing comes close to the shifter & i may trim it back as shown . Motor mount bolts all line up, but
because the frame bosses are the not the same on both sides in length they'll need
to be cut. What every i cut off, i will use on the other side, so the motor is centered.
The frame will need to be modified some near the existing air box mount, so the carb
clears, but it looks like there's more room then on the 81 frame in that area.

More to come, including looking a different Husky swingarms

Husky John

 

[Michel Dufayard]

You need to take the 82 mounts for the 82 frame.
510 monoshock head and 510 twinshock head are differents .
The angle of the carb with the head is different.

 

[ruwfo]

Michel,
not sure about the angle of carb on the monoshock vs the twin shocker, but with the airbox front mount
partly cut off the carb lines up with the use of intake spacers. I'll take pictures of the spacers & carb
fit , soon.
Husky John

 

[Michel Dufayard]

About the different angle between mono and twinshock, if you are not sure , I'm certain . The parts numbers are also differents.

 

[Michel Dufayard]

Compare the inclination of the boot and the distance of the fin with the boot.
First picture is a 510 twinshock head , 2nd is a mono (also in a 84 wrlc frame).

 

[ruwfo]

Now i needed to center the motor in the frame so the pipes will clear the front down tube. I measured
the distance of the original 86 frame's front motor mount bosses & then cut down the left side (shifter side)
of the 83 frame to match that dim. I then took what i cut off & sandwich them on the right side so the
motor mounts are now centered. Pipes now clear the front down tube & I only need to make rear mounting
pipe brackets/tabs.

 

[ruwfo]

After talking with Michel, he showed me how the earlier twin shock motor's head intake is tilted down slightly so the carb would
clear the rear of the main frame tube under the gas tank near the front of the seat. The later single shock bikes 86 and newer
don't have the intake tilted , so an adapter needs to made. I'm making a mock up piece to check what's a good angle & what's
the best distance to place the carb back enough. Here's an example of the adapter needed.

 

[Michel Dufayard]

Ingenious to cut the front motors mount bosses. But will the swingarm axle will go ?

 

[fran...k.]

Did the four stroke bikes in that era of frame have that not straight front tube? I seem to feel you are having pipe clearance problems due to that. The way the pipes come out of the head for an inch and then splice into a curved section is pretty crude on those and on it's "decendents" and even the up tite aftermarket I got with my 99. Well at least from what ones I have seen so could tampering with the pipe also work?

Aren't those differing length mounting tubes (the ones you cut and then used as shims) which go through centered for the center line of the motorcycle? Shouldn't you cut out most of that front tube and replace it with one from a silver frame? Why is that tube a little s shaped anyway the 500 two stroke fits into the silver frame? If you look at what happened to the four stroke when the Italians started changing things they used a forked bottom to attach to the frame bottom which contains the mounts similar to the water cooled two stroke left kicker but the forked portion didn't go much past the mounts. So you might be able to use a cagiva era four stroke frame as a donor instead of a silver one like suggested earlier. I generally make those front plates new out of quarter inch thick aluminum but the ones from a 99 te seem to be about three sixteenths inch thick steel.

5 minutes later. Probably the above suggestions might not be all that easy but my 1988 510 has a straight tube with the mounts and maybe so does the frame that engine came in. There probably is enough straight near the steering stops to use a vintage left kick two stroke water cooled one and shorten up the two small tubes as needed.

 

[ruwfo]

Michel,
Yes the swingarm, both fits in between the frame & the swingarm/engine pivot bolt lines up fine. The only thing i need to
make is a collar/spacer to go in the rear engine mount. This is because the pivot bolt on the single shock bike is slightly larger
in diameter, then the twin shock bikes. Picture shows a 1980 aluminum swingarm mounted up for a trail fit.