Category: Tech

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Yamaha Limited Pipe Specifications
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Yamaha Limited Pipe Specifications

By Lynn Haddock

The approved RLV PIPES for the Yamaha Limited Class (#17) are the VKA-K1, VKA-K2 and the VKA-SR-Y.

These are the same pipes as the older model KPV K1 and K2 and the WKA/IKF SR-Y. These are readily available in the used market.

The current RLV HEADERS are the VKA-9110 (12 degrees) and the VKA-9110 (straight). However, any straight tube header may also be used. No tapered tube headers are allowed!

The minimum length for all the pipes is 12″ from the piston face to the start of the first cone. For convenience, the edge of the fin just above the exhaust (see Fig. 1, below) is 2.4″ from the piston.

 

FOR THE 90° PIPE

For the 90° models (K1+K2), this means, in order to have a minimum distance from the piston face to the end of the connector tube as 12″, the connector dimension has a combination of 2.4” + 9.6” = 12″ (see Fig. 2, below).

 

FOR THE 60°/30° PIPE

Unlike the 90° model, the 60°/30° model has 2.5″ of distance is made into the 60°/30° elbow (see Fig. 3), so the distance from the piston to the end of the connector tube is 9.5″ (2.4″ + 7.1″) minimum (see Fig. 4) and the overall minimum distance is 12″ (2.4″ + 7.1″ + 2.5″ = 12″).

There is no maximum length for any header. The connector tube is 1.750″ diameter.

For information on the RLV pipes go to: www.RLVcatelog.com. On the left, at the bottom, click on VKA Vintage Pipes. This page with the 90° and 60°/30° pipes will come up.

RLV PIPE CLARIFICATION BY LYNN HADDOCK

Several questions have arisen regarding the RLV pipe and the proper installation. Below is a picture of the 90° pipe (Fig. A) and the correct, minimum length of the connector tube (Fig. B)

Figure A
Figure B

Fig. C shows the 60°/30° pipe, and Fig. D shows the proper installation of the minimum connector tube.

Figure C
Figure D
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History Lesson: Scott Kneisel Rebuilds the Mc8
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History Lesson: Scott Kneisel Rebuilds the Mc8

As we have changed over from the old VKA website to the current one, some of the links to articles and photos just stopped working. Ryan Courts made a PDF copy of Scott Kneisel’ss Mc8 rebuild article and put it up on the VKA Facebook page. Although most of the information is specific to Mc8s, Scott’s 2-stroke rebuilding techniques (measuring/installing seals and bearings etc.) apply to virtually all kart engines.

As we recover some of this “old gold” we will repost it in its respective category on the new site. However, in an effort to conserve space on our new site, we will simply have a descriptive paragraph and photo about the content of the article followed by a new link to where it is archived.

Comments and suggestions always welcomed!

Read / Download Mc8 Rebuild Article
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Saving Those Heads
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Saving Those Heads

How to Fix Destroyed Vintage Cylinder Heads

By Len Emanuelson

One of the real issues with running vintage kart motors is
that the parts are hard to find and are getting very expensive. There are a few
engines like TKM and a few IAME based engines that you can still buy new
replacement parts, but a typical cylinder head can be $250 or more. So it pays
to try to salvage what you have if you can. In most cases all that’s required
is a manual lathe and a $60 arbor from LAD.

I’m no machinist, but I have a lathe, and at the rate I blow
stuff up, I fix my own engines. In this case a friend brought me a TKM 150cc
cylinder head that had been pretty well beaten up by a piston failure. As you
can see in the “before” photo, we mapped out our strategy by numbering the
sequence of the surfaces to be machined. The objective is to end up with the
squish band the same relative distance from the sealing surface as it was
before machining. Another objective is to remove the least amount of material
possible, because it is the head’s total mass that acts as a heat sink, and
keeps your air-cooled motor cooling as efficiently as possible.

Follow along as we bring this cylinder head back
to life in less than one hour of time in the shop.

Step 1

First, inspect the damage to see if the head is even repairable without welding. We decided to first machine the cylinder sealing surface (#1) .020”, the head-to-muff surface (#2) .020” second and the squish band (#3) .020” third. If the squish band did not clean up at .020” we would have started over on all three surfaces with an additional .010” cut. The object is to remove the least possible amount of material and still restore the surfaces.
First, inspect the damage to see if the head is even repairable without welding. We decided to first machine the cylinder sealing surface (#1) .020”, the head-to-muff surface (#2) .020” second and the squish band (#3) .020” third. If the squish band did not clean up at .020” we would have started over on all three surfaces with an additional .010” cut. The object is to remove the least possible amount of material and still restore the surfaces.

Step 2

Here is the LAD cylinder head mandrel. It fits into the lathe chuck or collet and then the head screws on to the mandrel via the sparkplug threads.
Here is the LAD cylinder head mandrel. It fits into the lathe chuck or collet and then the head screws on to the mandrel via the sparkplug threads.

Step 3 & 4

Step3
The mandrel should stick out of the lathe chuck or collet just enough to screw on the head and clear the fins. This provides the least amount of runout for accurate machining.
The mandrel should stick out of the lathe chuck or collet just enough to screw on the head and clear the fins. This provides the least amount of runout for accurate machining.

Step 5

We first machined the head-to-barrel sealing surface. To do this we ran the lathe in reverse (clockwise) so that we could easily see the cutting tool. Important because the tool must cut all the way into the corner of the “step” for the liner. The cylinder must be very tight on the mandrel or it will unscrew from the force of the cutting tool.
We first machined the head-to-barrel sealing surface. To do this we ran the lathe in reverse (clockwise) so that we could easily see the cutting tool. Important because the tool must cut all the way into the corner of the “step” for the liner. The cylinder must be very tight on the mandrel or it will unscrew from the force of the cutting tool.

Step 6

Next we cut the surface above the muff. We ran the lathe in the normal rotation (CCW) for this operation.
Next we cut the surface above the muff. We ran the lathe in the normal rotation (CCW) for this operation.

Step 7

The angled squish band is machined with the “compound” part of the lathe. Foreign motors like the TKM, most Komets, etc. use approximately an 11.5-degree angle on the squish band. A good way to check the angle your compound (without the lathe running) is to touch-off the cutting tool on the inside edge of the squish band, back the tool carriage off .010” and then move the cutting tool to the outside edge of the squish band with the compound. It should be .010” away from the squish band if the compound angle is set correctly. If not adjust.
The angled squish band is machined with the “compound” part of the lathe. Foreign motors like the TKM, most Komets, etc. use approximately an 11.5-degree angle on the squish band. A good way to check the angle your compound (without the lathe running) is to touch-off the cutting tool on the inside edge of the squish band, back the tool carriage off .010” and then move the cutting tool to the outside edge of the squish band with the compound. It should be .010” away from the squish band if the compound angle is set correctly. If not adjust.

Step 8 & 9

Step8
After cutting the squish band the bowl-to-band parting line was still in pretty rough shape. We readjusted the cutting tool and took a light cut on the outside edge of the bowl area until the damaged area was gone.
After cutting the squish band the bowl-to-band parting line was still in pretty rough shape. We readjusted the cutting tool and took a light cut on the outside edge of the bowl area until the damaged area was gone.

Step 10

A piece of 400 grit sandpaper was used to blend the angle cuts and damage in the bowl area. Probably not how your shop teacher showed you how to do it, but as you can see in the finished photo, it works.
A piece of 400 grit sandpaper was used to blend the angle cuts and damage in the bowl area. Probably not how your shop teacher showed you how to do it, but as you can see in the finished photo, it works.

Step 11

The final check is to make sure the squish band is the correct diameter for your engine’s bore. We are using a 58.8mm piston, so the 58.85mm size is just about right. If your diameter is too small, cut the squish band deeper. If it is too big, cut the cylinder sealing surface some more. After you do a couple of these you’ll get the hang of juggling the dimensions for the desired results.
The final check is to make sure the squish band is the correct diameter for your engine’s bore. We are using a 58.8mm piston, so the 58.85mm size is just about right. If your diameter is too small, cut the squish band deeper. If it is too big, cut the cylinder sealing surface some more. After you do a couple of these you’ll get the hang of juggling the dimensions for the desired results.