Messages

Not bad, TZ750 Fairing H, J, K seat.  Daytona wheels

Mark,

How are you doing a long time no speak and yes I am envious... I agree with Oxford, given it's a C&J I would use the better forks.  once you get it assembled just take it to Bigley and have him do a set of pipes for you from a Swarbrick kit.

The RZ system is not as good as the RD, the detents can make it hard on the pawl, which would loosen the rivet/pivot.  The guys that stomp shifts tear them up (not accusing you of this) I reduce/round the peaks on the star wheel.

There is a modified shift drum that some of the road racers run, it puts neutral all the way at the bottom,  it can be a struggle to get the bike in neutral when you grid up, stalling on the grid is VERY bad... you get to start last. 

I had a chrome set of these on my RD 350 back in 78.  Called them sleeper pipes because they looked like stock pipes.  Not as good as Bassani's but definitely better than stock.  They were not much better than stock for ground clearance,  but neither were the stock pegs.  I lost the rear grounding the peg loop hauling the mail on a 270-degree entrance ramp to I-4, thankfully all I ended up with was a rashed right forearm and a scratched-up peg and pipe.

John has his own idea's good luck with the build.

I have been thinking about this and have the following suggestion IF you have the budget. 

1. I have built a full race (what some would call a stage 5) RD350 motor using 400 cylinders and it did very well.  I built it for Mark Morrow one of the fastest RD road racers for the past 20 years.  He is a MULTI MULTI time national champion.  He wanted to try and run an RD 350 against the 400's

Specs were stock 54mm stroke, 115mm 400 rods and a 66mm blaster piston displacement = 370cc's

I decked the top and bottom of the 400 cylinders to make them match up with the 54mm stroke.  In doing this it greatly reduced the port work because the 400 ports are already Taller because of the longer stroke so they had advanced timing on the 350 bottom end,  115mm 400 rods.  No spacer plate is required.   Because I used the blaster piston and the 115mm rod I took very little off the bottom of the 400 cylinders and enough off the top that it removed the top fin, this was simple machine work.

I had to reduce the 400 head CC's to get the compression right.  Mark won many races on it against the 400's but he had to work hard against the additional torque and power of the 400s (his riding skill did a lot to help).   He has raced many RD's both 350's and 400's, his words, This is the fastest 350 I have ever raced.

On to your project, if you find a builder I am happy to share details,  I would do as you hypothesized,  use the 400 cylinders sleeve them down to run a 60mm YZ 125 piston (it's like a blaster piston shorter pin to the crown than a 350/400 piston), I think its the same as an RD250 piston as they are also shorter pin to crown. 

If you can get a set of European 76 - 78 RD250 heads they are the same size as the 400 cylinders and the smaller combustion chamber will make it easier to machine them for the 310 CC displacement (larger than the older US-spec, I have 2 RD250 Daytona heads that also match the 400 cylinders, I might let one go).

I think this will yield the best possible results with the easiest path, all the machine work is very simple and straightforward, and it will be easier to port because of the 400 cylinders.  I would opt for aluminum sleeves with nickasil bores...


Fell free to reach out to be if you are intested in discussing this

I'm hoping s,  2.15" x 19" mikes wheel and spokes fit rd hub. Triple trees with a dirt track type tire on it.

You will want to work on shock length and fork position/length.  That larger wheel can upset the geometry and increase both the rake and trail.  I would suggest that you might find an 18" tire that matches what you want to run to make it easier to get the setup right.  (unless there is an issue getting spokes and an 18 inch rim at a similar cost to the mikes).

You want the rake at about 25 degrees and a trail around 3.625 - 3.75 inches.

A lot of good suggestions but the dynamics for a drag bike based on a 400 crank are not good, although it could work in the dirt.  it would be a long stroke motor given a 62mm bore and a 56.25 stroke = 308 cc's

There is a drop in Yamaha piston for that build, it is a YZ125 (period) piston, stock bore is 56mm so a first over would put you right there.  you will need the right pipes to make it work and as I said in the dirt it might work.

The alternative is to send a crank to Crankworks, they will stroke a crank at a reasonable cost. 

you can use a 2mm oversize YZ piston @ 58mm and get the stock crank stroked to 58mm which is a +4mm from stock and is a common stroker crank for a banshee /RZ, it is known to work well.

On a drag racer, I am not sure I would even lengthen the rod, I would use a  2mm spacer plate to even out the additional stroke.   A 115mm rod would increase the crankcase volume a little and 250's run well as a long rod configuration. 

Given you are drag racing there is not a lot of benefit to getting later model European 250 cylinders, they have longer fins and larger heads that are as big as the 400's and help with a road racer.  They run billet heads on drag racers with no issue given the short run time.

The advantage to stroking a 250 is that you don't get into a torker motor (long stroke) configuration

58mm bore X 58mm stroke yields 306 cc's

On a 62mm stroke (400 crank) with a 56mm bore you end up at 305cc's, the issue will be RPM and piston speed.

The reason I say it might work is hookup in the dirt.

I am not sure how big you can get a YZ piston BUT at 60mm you are at 305 cc's and there is PLENTY of meet to re-sleve  a 250 to get it at a 60mm bore.
This is the easiest way to get to the class limit and you know it works its just a slightly smaller bore than the 350.  This is the way I would go.

I just checked and there are 60mm YZ pistons available from multiple sources.




It will be EXPLOSIVE as coming on the pipe,  MORE than porting you will need the right pipe design.

Oxford is correct,  XS hobs are wider, they are the same as a TZ250/350.  I have a set of 34mm TX 500 forks (both lowers have disc mounts) and a TX dual disc hub that I would part with

E-mail me I have the chatter solution. (just info on causes, parts, etc.)

If you are interested in working the 202 MotoGP race in Austin check out the post in the racing section.

Thanks

If any of you are interested there are volunteer opportunities to work the MOTO race in 2020.  I have done it the past 2 years.

There are 3 positions you can work:

Track Marshal:   The guys that to get the bike if there is a crash and if you can help get it back on track, if not get it behind the wall.   

Flagger: self explanatory 

Rider assist:  you are the property of the EMT, your job is to do what the EMT tells you (stretcher bearer IF needed).  8)

When:  Thursday through Sunday (date is not yet confirmed for next year but it is in April)
You get 3 general admission tickets (you don't need them you can give away use for a friend or wife etc.)
You have to provide your own uniform unless you are accepted for rider assist.  Uniform is while pants and shirt.
You cannot wear anything branded (no VR46 hats or MM93, Ducati, Yamaha etc.  Depending where you work you will be on camera if there is a crash)
NO you can't video, when bikes are on track you have to be at your station.

You are responsible to get to the track and for all transportation to-from the track unless you stay at one of the hotels booked (your cost special rate) for workers in Austin, they include a shuttle bus to – from the hotel – track.
You can camp at the track in Lot M for free, it has hot showers and porta johns.
You get breakfast lunch and dinner every day.
You get Swag and prizes.
You are TRACK SIDE 
Friday Saturday and Sunday starts at 5:15 AM
Friday and Saturday end at about 6:00 PM Sunday at 4:30.
Thursday is training:  Get registered, Morning and a repeat afternoon training session.  Watch videos and you can participate in the afternoon track test if you can be there Thursday.
Friday is track inspection and certification by the FIM first thing in the am.
Then practice, more practice and more practice.  Moto3 Moto2 MotoGP and Moto America.
At the end of the day there is a pit walk.

I have been a marshal the past 2 years, first year as a corner lead (the guy with the radio headset, this year as a sector lead overseeing 3 flag positions, 2 marshal positions and 1 medical.

IF you have race experience it is HELPFUL,  I will be glad to talk to you and help with some pre-training that will put you ahead of the game.  I have really enjoyed doing this but it is an UNPAID gig.. it does put you in an incredible seat for the races.

If you have a bike and bring it you do get to do the track ride (SLOW LAP) of the track for free.
Please contact me, they need workers!!!!

Please drop me a PM or an E-mail if you are interested!