Author Topic: Racer Resurrection  (Read 39364 times)

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Re: Racer Resurrection
« Reply #20 on: February 02, 2015, 10:34:01 AM »
My cylinders were set up for a "zero deck height", the piston comes flush to the top of the cylinder. The RM85 pistons being shorter, the material was taken off the bottom of the cylinders (base). I run Tab Loc (pre-DG) aftermarket heads. They are high compression (somewhere I have notes!). The bike never ran with well set up this way so I made base shims and run it as I did before with the piston not coming up all the way and no head gasket. I really should find out the corrected compression ratio. After I get this crankshaft stuff sorted, I will get some heads done with a proper squish. I also have a box with a clutch that I had a Kawasaki KX125 clutch basket converted to fit the BS driven gear that is about 1 pound lighter than than BS clutch. I just need to finish it!

paul

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Re: Racer Resurrection
« Reply #21 on: February 03, 2015, 08:07:45 AM »
My thinking for cutting the top off the cylinder instead of the base was that, with the shorter piston, the port opening/closing point was increased by .035" on all the ports. I don't know if that was good or bad, but that was my reasoning. I still opened up the exhaust port more anyway.
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline al_pritchard

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Re: Racer Resurrection
« Reply #22 on: February 03, 2015, 09:48:56 AM »
Paul - I’d be very interested in seeing your notes around your head design. One concern I had with the BS head, is it doesn’t seem to have a lot of meet in the dome. And I didn’t want to cut to deep into it.

I would have assumed the same as Karl regarding taking off material from the base of the cylinder.

I’m still a little new to this engine tuning and measuring. But needing as a place to start I had a session with the degree wheel this weekend. I don’t know if my ports are stock, or if Dave made any modifications to them. But the rotary inlet port in the side of the case has been modified.

Sorry, my degree measurements were horifiy wrong, so I've removed them to prevent confusion. I'll re-measure this weekend and re-post.
« Last Edit: February 03, 2015, 09:04:16 PM by al_pritchard »
Al Pritchard
Highlands, NJ

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Re: Racer Resurrection
« Reply #23 on: February 06, 2015, 12:30:33 PM »
Hi Al,

I will look for those notes. I think I mainly checked the volume of various heads I have. I've had a couple sets of stock milled similar to Karl's. The TabLoc heads came with a squish but they are 1960's technology. I have a set that I got from an old racer that look like they were welded up pretty nice and a proper squish cut. However I haven't measured the volume yet and a bunch of the fins got broken off in shipping. One of the other things on the list of mods is to have some heads done to with a proper squish. If you want to give me a call with questions 619-675-4060. I'll dig up my timings or at least what I have written down somewhere.

paul

Offline al_pritchard

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Re: Racer Resurrection
« Reply #24 on: February 06, 2015, 03:06:30 PM »
Thanks Paul,

Heads will be the next serious investigation for me. I wanted to get the cylinders out of the way first and work the heads while they were sent out. I'll take you up on your offer for a call soon.

In the mean time I spent some time with the degree wheel and a nice pint last night. Looks like I’v got a "half-speed" alternator. Good to know as I start looking at options for an electronic ignition.

In preparation for having my cylinders nikasild I wanted to better understand the current port timings, and make any alterations. This includes decking the cylinder based on the heigh of the new pistons, and any alterations to port sizes.

An interesting thread over at NATs on a 350 GTR is talking about  adding transfer gullies between the transfer ports and host port. They mentioned the yamaha TD1-C had a similar setup. It’s considerations like this that I want to take into account before sending off the cylinders to be nikasild.

Along with the port timings below, I’v also done my best to measure the ports. Take it with a grain of salt - I’m sure I’m off by a square mm. But this is what I got.

Port Measurements
Exhaust Port: 501.5 sq mm
Transfer Port 1: 154.5 sq mm
Transfer Port 2: 154.5 sq mm
Boos Port: (need to do this still)

Piston Timings
92° ATDC - Exhaust Opens
112° ATDC - Boost Ports Open (opposite of exhaust)
116° ATDC - Transfer Port Opens
158° ATDC - Bottom of Transfer Ports
170° ATDC - Bottom of Exhaust Port

180° ATDC - BDC

192° ATDC - Exhaust Port Bottom (12° PBDC)
206° ATDC - Transfer Ports Bottom (26° PBDC)
246° ATDC - Transfer Ports Closed (66° PBDC)
250° ATDC - Boost Port Closed (70° PBDC)
270° ATDC - Exhaust Port Closed (90 ° PBDC)

* The bottom edge of the transfer port is cut below the piston top at 90° BDC.

Rotary Timings
40° ATDC - Rotary Inlet Port starts to close
76° ATDC - Rotary Inlet Port fully closed
222° ATDC - Rotary Inlet Port starts to open (24° PBDC)
280° ATDC - Rotary Inlet Port fully open

And because we all love photos.

Cylinder Rubbing




Checking my work


And rechecking my work


And the port maps and measurements

I could not find graph paper with one square equal to 1mm. So I scaled the drawing up, it’s a little easier that way actually. The larger square makes it easier to count.



Al Pritchard
Highlands, NJ

BS175 Racer

Offline al_pritchard

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Re: Racer Resurrection
« Reply #25 on: February 06, 2015, 03:54:28 PM »
Forgot to add the port map. Again, I’m sure this is not 100%. It was my first time doing this so I suspect I’m off just a little.




Al Pritchard
Highlands, NJ

BS175 Racer

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Re: Racer Resurrection
« Reply #26 on: February 07, 2015, 12:48:05 AM »
That's funny,

Gerrit from the NL and I are the ones talking about the added ports on the NATS site. My thought was to add another port between the transfer and boost port that feeds between the two. I also thought of welding up the transfer base and making the transfer bigger to feed the added port between the boost and transfer. My problem is I have no idea if or how it would work. I think I've seen something like it in another cylinder at some point but don't remember what bike. Like you, I try to plan as much out beforehand. I can give you a pretty good list of things that need to be improved before you spend any cash on making it faster!

paul

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Re: Racer Resurrection
« Reply #27 on: February 07, 2015, 10:13:39 AM »
Here are photos of SR cylinders and one of the pistons off my 175 roadracer with added port area. I don't know who did this work, I ended up with them on the bike when my brother Jim helped resurrect it in 2002 from storage after 25 years in the barn. He rode the bike to 2nd in 200GP at the Daytona AHRMA races in 2003. Additional area could be obtained by ports between the transfers and boost as you're discussing. Unfortunately, these were damaged during the 2004 season and I went back to modified standard cylinders.


Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

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Re: Racer Resurrection
« Reply #28 on: February 08, 2015, 11:13:34 AM »
Wow Karl,

Thanx for posting pics. I've seen finger ports added to cylinders over the years but never anything like that!

paul

Offline Gerrit

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Re: Racer Resurrection
« Reply #29 on: February 09, 2015, 05:21:09 AM »
I am at a loss to explain how these extra channels could work positively. While they do add transfer passage capacity, the streams are directed in a purely vertical direction and would disrupt the flow pattern from the mains and booster in my opinion.
I was thinking of extra gullies between mains and booster, like the gullies Yamaha added to the TD1-C cylinders. These did work on a TD1-C and were 12 mm wide and about 3 mm deep. Unfortunately I have never had my hands on a TD1-C cylinder to measure the gullies for both dimensions and flow direction. The distance between mains and booster on a GTR is about 15 mm chordally according to a quick measurement, so there is space to add gullies which are 10 mm wide. Whether they would have a positive effect on power is quite another matter, however.

Offline OldSwartout

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Re: Racer Resurrection
« Reply #30 on: February 09, 2015, 09:47:40 AM »
I agree Gerrit, the flow disruption might be detrimental.  However, the bike ran pretty good that weekend. He was only beaten by Dennis Poneleit on his Honda 175. Dennis, in his 70's, is still winning the AHRMA 200 GP class on that same bike bike 11 years later.
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline al_pritchard

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Re: Racer Resurrection
« Reply #31 on: February 10, 2015, 09:07:53 AM »
Paul I would be very interested in seeing that list.

A fare amount seems to have been done to the bike based on the Bridgestone tuning book. But I think some could have been done a little better. So any guidance would be very appreciated.

Karl, thanks for posting those cylinders. My wife happened to be looking over my shoulder when I was reading you post. As she often does when I’m looking at bike stuff - I think it’s to keep me from spending to much. Her comment was “Holy s*$#, you need to do that? Seems a little risky.”

The idea of adding something similar to the “S” port of the TD1-C is interesting. They mention the cooling benefits to the cylinder by allowing the trapped gasses to move out more efficiently. Being replaced with fresh cool gas. There is the oiling benefit to the to pend bering to think about as well.

I wonder if our RM85 piston will allow for the additional port. I’m out of town so I can’t look at all the parts, but the RM85 has a recess just above the ristpin. And use the TD1-C style port, the piston needs to have a port added.

(I’m still new to all this, so I tend to follow established patterns at this point. If you don’t think the port in the piston is necessary please tell me. Just be prepared for me to ask why.)

I couldn’t find any pictures online of the TD1-C but my copy of Yamaha Two Stroke Production Roadracing Motorcycles by Greg Bennett has a chapter with a couple of images. (I highly recommend this book by the way. Loaded with detail on the production bikes.

Lets start with the TD1-C Cylinder

Not the best pic, but you can see the “S” port in the upper right of the cylinder

And it’s matching piston


The book also has a picture of a “special” cylinder and matching piston. This cylinder had “A very rare TD1-C cylinder. Note the transfer port directly below the secondary transfer rather than an open S-shaped boost port which was the case with most TD1-Cs” (quote from above book.)

TD1-C “Special” Cylinder


And it’s matching piston


And the TD1-C Port Map



The port map and cylinder pictures are from the above mentioned book that can be found at http://www.tz350.net/yamaha_two_stroke_production_roadracing_motorcycles.htm


Al Pritchard
Highlands, NJ

BS175 Racer

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Re: Racer Resurrection
« Reply #32 on: March 03, 2015, 10:01:30 AM »
Hi Al,

here is a copy of what I sent to a guy in New Mexico that is building a couple of Bridgestones for customers. Sorry I didn't get back sooner. I got the rods I ordered from the NL and they aren't what I thought they would be. Also the place I was going to use in AZ for the crank work (Crank Works) is backed up with the start of the new race season. I'm probably just gonna use a back up stock crank until I can figure out a permanent fix.

    

   

Joe Ackley
Hi Joe,

Here is a picture of the rotary valve covers that I had done. Originally the Bridgestone covers are not equal length. I had these made to be the same length. If you modify stock ones you can probably make them the same length. If you want to run a Dyna ignition off the crank you would have to modify the rotary cover. The other photos are of a bike that was raced since new by Dwaine Williams. He did lots of mods over the years. Sadly he passed racing his Norton at Barber in 2007. As you can see of his bike, the carbs can get out there pretty far.

The last pics are of my bike with MX100? Yamaha carbs (22mm) and a shot of my current ignition mounting. I guess there are a lot of mods that I due that i just don't think about.

Add three extra clutch springs to keep clutch from slipping. I work at a Jaguar shop and I found a spring from a V8 cam tensioner that slips right over the Bridgestone spring.

I replaced the pins in the shift forks with solid ones and hand ream them to fit. Pain in the ass but at the time I was having all kinds of transmission problems.

Gears have all been undercut.

I had a new shift selector cam gear made to have more  positive shift. I copied the profile from a late 90's Zx10 kawasaki and had it altered from 6 to 5 speed. Then I had someone draw it up (then had some samples water jet cut) and we varied the profile to have a couple of different peak heights. I went with a pretty aggressive one and added a roller bearing like the ZX10.

I run Suzuki RM85 Wiseco pistons (806M05000) that are 50mm. This is an oversize for the RM but the same size as stock bore for 175 Bridgestone. I have Millennium Technologies Nicasil plate the cylinders. I run them just a tad looser, wiseco recommends .0020 clearance, i use .0025.

I've broken several cranks. A friend and fellow Bridgestone racer Karl Swartout (engineer) had some new center crank pins made a few years ago. This was to fix some of the broken cranks we had. I broke one of those last year. The pin is orig part of one half of a center flywheel. He had pins made and bored out the broken center pin. These pins were stepped and the same thing happened. Usually due to the bike running one one cylinder. The new idea is to have a straight 20mm center pin made and eliminate this problem. I talked with Scott Clough yesterday and he was probably going to use the same guy for the cranks. I'm waiting on rods from the Netherlands (Pro-X 1981 RM125)  before I can get started on the crank. The Bridgestone rods are great. The big end bearing kinda sucks though. The rm125 rod is same dimension except for being wider top and bottom. I want to have the material taken off the crank wheels and retain the nice silver cage bearing. I want to take material off the top of the rods to still use the RM85 pistons.

I have had rear sprockets done from a couple of places. PBI should have the profile on file. I use stock front ones (14,15,16) and I found a 13 from something else that I use on really short tracks. I have rears from 34-44 and the way the ratios are, I never use anything below 38 and the chain would hit the brake hub with the 34-35.

The stock brakes are not bad. I've had the brake shoes relined at a local place with two different materials. One is like a standard heavy truck brake lining. The other has a metal weave that takes way too long to bed in and is pretty aggressive on the liner. The bridgestone front braked fine but it was machined thinner (I run 32mm Ceriani forks) and it broke once racing at Barber. I run a Honda CB450 Black Bomber front hub now. It has enough braking to lift the back wheel under heavy braking.

As above I run 32mm Ceriani forks. I had the stem modified to fit the Bridgestome frame and run tapered bearings from ALL BALLS.

The front rim is WM1 40 hole (CB450 is 40 hole) and the back is WM2 36 hole with standard Bridgestone rear brake. There are two types of rear brake hubs. Mine is the 6 hole pattern for the sprocket. There is an earlier version with a separate hub carrier that has only a 4 hole pattern for the sprocket.

I currently run a Bridgestone BT39ss 2.50x18 tire on the front and a Heidenau 2.75x18 on the rear. i use to run the Bridgestones front and rear but they really heat up and the tubes can't take it. I may switch to a Heidenau 2.50 in the front sometime this year.

I had a custom aluminum seat and tank made by a guy in the UK back in 97. Sadly he retired. His workmanship is unbelievable and his prices were cheap! I ditched the seat because it kept breaking. It is very similar to an early Yamaha TD/TZ seat. Kent at Airtech made a fairing, seat and tank for a 175 a few years ago. That is the seat I have now. I really need a new fairing as mine is the original Harley Sprint (as supplied from Rockford Motors) one that has been repaired many times. My tank was very long like the bikes of the 60's era. I had it shortened by a good bit to get weight over the front more.

If I think of more stuff which I'm sure I will, I'll shoot off another email. Feel free to ask anything you may have questions about.

paul

Offline Gerrit

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Re: Racer Resurrection
« Reply #33 on: March 07, 2015, 09:23:38 AM »
The extra ports in the special TD1-C cylinder are similar to those in the TR2.The only way to get something similar in GTR cylinders is with completely new castings, or bore out the standard cylinder, carve the passages in and add a sleeve with the extra ports, either cast iron or aluminium. The latter, of course, needs a nikasil coating.
An alternative shape to that of the extra transfers of the TD1-C is that used by tuners in the UK for the Greeves Silverstone; they added a third transfer port above the intake which had, roughly, the shape of an inverted tea-cup handle. I suspect that this shape gives better control over the direction of the gas stream than the TD1-C type gullies. I think I may have a sketch or drawing of this arangement somewhere.

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Re: Racer Resurrection
« Reply #34 on: July 22, 2015, 09:58:28 AM »
Hey Al, I see you joined the NATS list. How's the project going? I haven't had any time for anything! Haven't found any other Bridgestone notes especially the ones I'm looking for with the jetting on a previous carbs set up. Getting ready to go race at Miller in Sept and Barber in October.

paul

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Re: Racer Resurrection
« Reply #35 on: August 14, 2015, 09:59:03 AM »
Hi Paul,

Progress has been slow over the summer. I’m working on a project up in Boston , so traveling back and forth from NJ has had an impact on my “velocity”. That and Iv been waiting for the new tank and fairing show up. When I order it, I thought it would only be a couple of weeks - it was a tad longer. Should be able to fit all the big parts over September, and get the cylinders set out for boring, porting and platting.

Also been talking with Karl about getting a set of his pipes and rotary covers. The pipes I have look similar to the tuning recommendation, but they are rather beat up.

On the subject of fairings and tanks. How has everyone been mounting them? The PO of my frame welded a tube across the top of the frame. You can see it just above the engine. The problem with this, aside from not knowing if it will align wit the fairing is it prevents you from pulling the head of the engine without removing it from the frame. Not an ideal.

Not the bar in the upper right
IMG_2255 by Al Pritchard, on Flickr

Also picked up a set of forks
IMG_2157 by Al Pritchard, on Flickr

The old ones are a bit rusty
Untitled by Al Pritchard, on Flickr

Paul, I think you mentioned on a separate thread you had to turn down the steering tube to find a bearing that would work. I may need to pick your brain on that as well. Once I get the old forks off and get some measurements.
Al Pritchard
Highlands, NJ

BS175 Racer

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Re: Racer Resurrection
« Reply #36 on: August 22, 2015, 09:13:48 PM »
Hey Al, good to hear from ya. Mine has some tabs with captive nuts that we welded to the frame tubes going down to the swing arm. From there ears go forward to a tube that goes out to the fairing. The first attempt broke many times from vibration, crashing etc. Finally welded some tubes at a 45 to the plate and tube and they've never been a problem. I can get the heads off with no problem but still have to take the motor out to remove the cylinders. I also don't have a battery box and my sump sits right about there. Funny, I have the same tommaselli clipons with shims (35mm) for 32mm. If I remember, the bearings from ALL balls were close and we just had to skim the ceriani stem. You have a different set of forks than me. I'll look and see if I have any pics to post. Damn, the inlet port in your cases looks huge!

paul

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Re: Racer Resurrection
« Reply #37 on: August 28, 2015, 10:20:51 AM »
Yea, I'm a little worried about the port size as well. I' also very worried about how tall the port is. It's hard to see in the photo, but the arched top is very close to the top edge of the rotary disk. Air leeks may be a problem. But I'm working with what I started with, the PO had opened the ports up already. Although they weren't exactly round and smooth.


The New Port


The Old Port, Overplayed


Outlines of Both Ports


Worst case is I need to make custom rotor disks to modify the open and close intervals. Or a new case.

In other news, parts arrived!

I'm slowly taking over my wife jewelry studio.
Al Pritchard
Highlands, NJ

BS175 Racer

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Re: Racer Resurrection
« Reply #38 on: August 28, 2015, 11:50:41 AM »
Is the fairing and tank from Airtech?

paul

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Re: Racer Resurrection
« Reply #39 on: August 28, 2015, 05:26:49 PM »
But I'm working with what I started with, the PO had opened the ports up already. Although they weren't exactly round and smooth.

Worst case is I need to make custom rotor disks to modify the open and close intervals. Or a new case.


No need for a new case or worry about custom rotor disks.  Just use JB Weld to build up material where you need it and rework to what you want.  Rough up the surface with coarse sandpaper, maybe drill some shallow small diameter holes in the surface and fill with JB Weld, rework to the shape you need.  I've used it with good luck.  And if it breaks loose for some reason (unlikely), it is not as hard as aluminum and the engine will probably just eat it with no bad results. It's good for 250° F or higher, which exceeds the intake temps you'll get.
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

 


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