Ty350

[jse]

Before and after photos of an 85' TY350 I built for a friend:

[marky g]

Nice work jon, what kind of paint did you use? does the plastic tank affect the finish of the paint?

Couple of pics of my latest project.

I've already cut the std foot rest's off and welded wider/lower one's, I plan to do a total stripdown and rebuild, engine will have new mains/seals, new rod kit and a rebore etc etc.

I've had about 6 TY 250's over the years, i love em!!!!!!! this one will be a keeper....the only job I can't afford just yet is a wheel rebuild....

Edited January 13, 2010 by Marky G

[marky g]

You know your stuff Jon, cracking Job.

Your right, I've got my work cut out to be fair the parts that are needed i would have replaced anyway, all the bearings seem very good with no play, even the swinging arm spindle came out easy all greased up.

I plan to keep this one so i don't mind spending a few quid getting it as I want, I plan to ride it in the isle of man two day event in 2010, a friend has got a pinky so it should be a laugh........here's the last one I had and restored.

[jse]

You know your stuff Jon, cracking Job.

Your right, I've got my work cut out to be fair the parts that are needed i would have replaced anyway, all the bearings seem very good with no play, even the swinging arm spindle came out easy all greased up.

I plan to keep this one so i don't mind spending a few quid getting it as I want, I plan to ride it in the isle of man two day event in 2010, a friend has got a pinky so it should be a laugh........here's the last one I had and restored.

Nice work!

Jon

[jse]

Here's a photo of the cast one-piece manifold/reedcage off the bike:

[neil king]

I just picked up a '86 that is in almost like new condition. Some mods were done at K&N in Tulsa. The head was worked on and porting, boysen reeds, something done to the flywheel, and something done to the rear linkage. I'm scared to ride it! It's been in a garage for 20 years. He put fresh gas in it periodicly ran the motor a little, the drained the left over gas out. And kept it clean. The clutch action is almost as good as a modern bike! Damn I wish it had 2 shocks on the back!!!

[neil king]

New toy

[jse]

New toy

Very nice! The 86 differed from the 85 in two ways: The 86 rear shock has a remote reservoir and the rear sprocket is smaller due to a change in the primary gear ratio (the crank gear/clutch hub gear ratio) to provide better clearance in the rocks. We ride them for fun as there is no class for them in most clubs here. It's not a twin-shock so it has to compete in the modern classes. Maybe we need to start an air-cooled monoshock class?

Jon

[z09]

Hello to all! Can you tell me about lightening the flywheel on a 1985 TY 350? Just picked one up that has some mods( reed cage mod with two stage boyesons,Works Performance shock,PVC fork spring spacers,clutch arm extension,etc) It doesn't seem to peppy though. Also, what's the preferred peg relocation technique? Thanks in advance

[jse]

Hello to all! Can you tell me about lightening the flywheel on a 1985 TY 350? Just picked one up that has some mods( reed cage mod with two stage boyesons,Works Performance shock,PVC fork spring spacers,clutch arm extension,etc) It doesn't seem to peppy though. Also, what's the preferred peg relocation technique? Thanks in advance

The 1985 TY350N was a little different animal than the TY250s available in Europe. For instance, it used the 8-petal, steel-reed cage with no "stuffer" that really killed intake velocity and affected low-RPM carburation. That, coupled with the huge mass of the crank assembly and the larger piston made it fairly "wheezy" in the throttle response department. The crank assembly was designed for the big-bore MX bike and in addition a thick steel band was shrunk-fit on the flywheel. A lot of riders have the band machined down to reduce the rotating mass. Some cut it off completely but I've found that machining about half the thickness seems to work better.

There are several ways to relocate the pegs. I cut the peg bracket off the frame tube and made a 1" extension, rolled from mild steel to drop the pegs lower and back. Adding a serrated strap of steel to the back of the stock peg locates the sole of the boot further back as well as widening the peg for comfort and the combination has proved just about right.

Jon

[z09]

Great info! Are the pegs about 1 inch down and 1/2" back? Also a gent pm'ed me saying he had a lightened 250 flywheel for sale. Are AC/mono TY 250/350 flywheels interchangable? The bike I bought has some mods, but does anyone have before/after photo's of modded heads or flywheels( mine may already have been done...)

[jse]

Great info! Are the pegs about 1 inch down and 1/2" back? Also a gent pm'ed me saying he had a lightened 250 flywheel for sale. Are AC/mono TY 250/350 flywheels interchangable? The bike I bought has some mods, but does anyone have before/after photo's of modded heads or flywheels( mine may already have been done...)

ZO9,

Thats about right on the peg relocation.

I'm not sure about the 250s, the U.S. got the 350s exclusively from what I remember (we tend to like engines large here, in spite of our inability to handle them at times) and may be the only ones with the extra flywheel weight band attached. I'm sure our UK buddies can answer that.

The 350 had a trapizoidal shaped shaped combustion chamber which was the rage at the time (it was designed to reduce overall surface area in the chamber). The chamber design was not too bad but the excessive squishband clearance was the problem. Most of the 350s I measured ranged from .084" to .097"+ and should be in the .039"+ area. Some riders removed the thick copper gasket and used sealer to secure the head to the cylinder in order to tighten up the clearance. This technique was not unusual and we used it often in the roadracing two-strokes at the time.

The problem with excessive squishband clearance is, you essentially have two combustion chambers. With too much fuel/air trapped in the squishband, the spike in pressure/heat when the plug ignites the center chamber tends to autoignite the fuel around the outer area of the piston crown. This results in the familiar pinging ("pinking" outside the U.S.) of the 350s. Pinging carried to extreme is detonation, which is a real engine killer.

Probably a better way to re-set the squishband clearance is to get some very thin copper sheet (hobby stores carry some) of say .003-.006"" and make a new gasket. I've re-machined my chamber to a more effective hemi design (the shape and volume goes along with the different porting arrangement of my cylinders) and along with the .003" copper gasket, it brings up the clearance to .040".

Jon

[z09]

Jon, It looks like you machined the "lip" all the way off of the head. Do you run the thinner head gasket with that? Your head does have much more volume in the bowl than mine. Could I run both mods(lip removal & thin gasket) with my stock head? Could you explain your porting and pipe mods also? And why do you like some flywheel left on as compared to complete weight band removal?

I'm not wanting to go too crazy but my old "73 Bultaco Alpina 350 was a torque monster compared to this TY in it's current state.

This bike sat probably a decade before I got it. How would I know if my crank seals are leaking?

Jeff

[jse]

Jon, It looks like you machined the "lip" all the way off of the head. Do you run the thinner head gasket with that? Your head does have much more volume in the bowl than mine. Could I run both mods(lip removal & thin gasket) with my stock head? Could you explain your porting and pipe mods also? And why do you like some flywheel left on as compared to complete weight band removal?

I'm not wanting to go too crazy but my old "73 Bultaco Alpina 350 was a torque monster compared to this TY in it's current state.

This bike sat probably a decade before I got it. How would I know if my crank seals are leaking?

Jeff

The lip is machined off, but the squishband is also re-machined up into the head. I run the .003" copper gasket with this head. The volume in the center chamber is deceptive when compared to the stock, cone-shaped chamber as the "roof" of the chamber has also been dropped due to decking the gasket surface (removing the "lip"). You could possibly run the lip removal and thin gasket, but you will need to check the squishband clearance carefully and each cylinder/head is different due to manufacturing tolerances.

The porting is different due to wider/re-shaped ports (increases bottom/mid-range torque) and the port timing is "staggered", in that the rear boost-port opens first, rear transfers second and front transfers last, which promotes better scavanging of the cylinder. The exhaust port is widened and re-shaped accordingly.

The pipe is slightly larger in diameter for better volume and slightly longer to promote mid-range torque.

Leaving on a certain amount of flywheel band smoothes out the power and is much better for traction in some sections, such as a muddy uphill where you can roll on the throttle to get quick response where the traction is good and then use trailing throttle (and flywheel) to roll over the bad spots and still get good bite from the rear tire.

Jon

[z09]

Wow! Nice explanation! Good job on the motor work. I'm looking for piston and rings for a top end job and my favorite online source doesn't show any availiblility. Are parts availible? Maybe another bikes rings? Also I got some modification info from 1996-1997 about things guys were doing to their TY's to make them "Super TY's". This includes carb mods,swingarm extensions,fork mods,linkage mods and frame mods(!) to reduce rake. I could post some if anyone is interested. Quite a bit of stuff!

Are those Talon brakes pretty rare? They look tempting...