Sunday, October 31, 2010

close shave

The FCR parts from Sinceros Speed Works have come in.  These are the jets, needles, and intake bell required to convert the 39mm carb originally off of a yzf426 to work with the DRZ -- essentially the same carb as sold on the E model DRZ, and also available as at kit for $500 or so.  I spent considerably less; here's hoping it works as it should.
You can see that this carb has provision for a throttle position sensor, which I am told is not supposed to be hooked up -- makes sense, as the carb was originally from a Yamaha.  Idle wheel can be seen to the lower left; red knob is for a hot start -- very important when MX'ers crash during a race and need to kick-start the bike in a hurry while warm.  Black knob is the choke.

Like all MX throttle cables, what came with the bike is far too long.  Will leave it as-is for now, and try to track down some brass ferrules in order to make a short cable of the proper length.  Ran out of them with my earlier Venhill kit I got from the UK.

Only one cable is needed, as the return spring action of the slide is considerable.  Not sure if I should bother covering the upper hole, as I don't intend to get a lot of dirt in there!

This is where the "close shave" comes in -- the lower bolt on the float chamber misses the frame tube by 1/2 a millimeter!  The whole conversion would have been a big "fail" had my welding or the carburetor forging been microscopically different.  Result!  According to all the experts, this mod alone should be good for a couple of hp.  Just need to get the jetting right for my application and altitude.  Won't bother trying to run it till the spring, as it is below freezing regularly these days.  Fettling on this bike is done for now.

Wednesday, October 27, 2010

Swarf and inspiration

Atom-Jet is making me the two spacers, and so I attacked the rear subframe, cutting off about 5-6 lbs in the process.  I shoulda done a before and after weigh-in. But here's where I'm at right now.  I had some 3/4" 4130 left over, so I replaced the passenger area and luggage rack with just the cross-member seen at left.
A lot of time was spent with the angle grinder, first cutting off large chunks of metal and then grinding off the remains.  There is more that could be done, but I wanted to stop here before I went any further.  Depending on how the tank fits, I might need to adjust the angle of the subframe, or add supports to prop the seat section up a bit.
I've also been looking online for some inspiration -- some sort of neo-retro look for the bike.  Over the course of the project, my ideas will likely morph and change, but here's a neat Hawk I found while researching fuel tanks.
I can see it has a 125 GP seat on a custom subframe, and the tank was molded from foam and wood -- not clear if it is covering an aluminum tank underneath... not keen on using a fibreglass tank on a streetbike.
Speaking of tanks, I think I found something that should work with my frame.  As usual, its from a bike never imported official to North America... so I found it in Germany, sold to me by a Dutchman living there.
From a bike called a KR1S -- a 250cc 2-stroke that battled with RGV250s and RZ350s in Europe back in the 80s.  A bit rough looking, but comes with a cap and petcock, and rubber bumpers for mounting.  Hopefully it gets here in one piece and is suitable.  The original tank is too small, ugly as sin, and wouldn't work with my oil in the frame idea...

Sunday, October 24, 2010

another new project

I'm addicted, I guess.  Better than crack and only slightly less expensive.  Embarking on another 'mono project -- this time, for the street.  Plan on using the DRZ/KLX engine again, as I have a bare engine for mockup purposes, and a few spares and extra hardware that I can use... as well as experience with the engine. 
As for the frame, I am starting with a Muz Skorpion frame that I got off of ebay.  The Muz was normally powered by a Yamaha 660 single, so the smaller DRZ will fit in with no problem.  I also got a subframe for the engine, but its about 10 lbs heavier than need be -- for a passenger, as well as to accomodate luggage and two exhaust pipes.  No thanks.  The angle grinder and cutting wheel will get some use.
I also found a DRZ rear swingarm for $14 -- this is the S version, so I want to find an SM for the final version -- a bit shorter, with proper streetbike axle blocks.
As for how the back end will be suspended, I'm thinking of going retro with twin rear shocks, or perhaps a single offset rear shock a la Norton rotary racer or ducati sport classic.
Allegedly a R6 front end bolts on fairly easily... I have acquired a set of 99-02 front forks (the RSU version), and a front wheel with twin discs for only $19 (the forks and triples were just over $100).
As for what the final "look" of the bike will be, I'm not 100% sure on that -- while a complete idea should be in place prior to the welding bottles being opened up, there are some mechanical things I need to develop or create, that I want to put into practice on this bike.

The first involves the oil tank.  I need a minimum of 2 L of oil for the dry sump engine.  What I would like to do is "hide" it, by incorporating it into the frame.  The DRZ400 dirtbike did this with a rectangular downtube on the stock chassis.

You can see engine mounting tabs just aft of the steering head.  The idea would be to use a 2.5" OD tube (with some jiggry-pokery to get the right volume) to mount to the front engine mount on the frame.  One would bolt to the other, and then the proper fittings would allow the hollow front engine mount tube to act as a oil tank as well.  The rad would mount to that, and etc, etc.  Of course, before I do any of that, I need to mount the forks in place, and create a "rolling chassis" -- need to get the angle of the dangle of the rear swingarm, and finally determine how long the front engine mount will be.  You can see some old 2.5" tubing in place for mock-up purposes already.
When dad delivered the frame and parts this past weekend, we also drilled out the frame engine/swingarm mount hole to 17mm -- even had a nice bolt at the right length hand I can use.  As you can see in the pic, a few spacers need to be made to center the swingarm (and ergo, the engine) in the frame.  I've got some nice aluminum alloy material to start with.

This can hopefully be an ongoing project to play with over the next few years... I'll keep everyone posted with updates as they come in.

Sunday, October 10, 2010

Swingarm Swap

Started the process yesterday to switch out the steel ex swingarm for that of the versys.  Old rear swinger cam out fairly simply... and it looks like more of the parts are interchangable than originally planned, which will save me some money in the swap.  Did some comparison of part numbers on, and I already have $60+ of reusable parts, in the form of spacers, oil seals, etc.  I still need to order some items, but it will be far cheaper than I thought.
 While I was at it, I also removed the front countershaft sprocket.  I have a leftover racing chain with low miles that is slightly shorter than stock.  My hope is to shorten the gearing for racing, but go to a 13-43, rather than the stock 15-46.  The original chain had to be cut off anyway, so I went with a 520 set.  For longer tracks, I will switch to a 14-43, essentially back to stock gearing, but with the smaller sprockets overall.  Dad's bringing those in for me in a week or 2.

The bike is held up by a stand that I originally built to pass through a hollow rear axle -- this time, I just put a 3/4 inch tube through one of the hollow frame spars, and it lifts the back end up without using a rear stand.

The shock will also be sent out for a rebuild and revalve -- not sure whose weight it was set up for, and it is also weeping a bit around the seal. 

Note how much more beefy the rear swingarm is from stock -- and its still 4 lbs lighter!  Rear brake caliper hanger and caliper, along with the rear wheel spacers can be reused.