Author Topic: RD350 Track Bike build  (Read 45776 times)

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Offline 5port

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Re: RD350 Track Bike build
« Reply #15 on: June 09, 2020, 08:17:26 AM »
Personally I think adding a dry clutch would just be a massive waist of money really, you won't be doing any push starting anyway, or will you ?

Yes, I think the real dry clutch would be overkill on this, and not needed.  Mind you, I might yet win the lottery! :D
Push starting?  ::). Actually, I am aiming for no kicker.  :)

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Offline german

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Re: RD350 Track Bike build
« Reply #16 on: June 09, 2020, 11:10:46 AM »
Good read so far, Chris :)
The 2R8 crank has sloted rods as standart.
At the moment I am collecting parts for a track/fun bike like what you do. In fact I have to collect the parts in my sheds.....so it is more a search where they are lying :-\
I am going the dry clutch route with the RD gearbox. I have a long shaft for the RD gearbox for useing the TZ clutch, clutch case etc.
I do that only as I have the parts lying around, no need to do it because of the power output. A RD clutch is good enough to cope that.
Cylinders will be Fahron tuned R5 ones.
Regards Uwe
Classic Racers do not hide the ashes, they keep the fire burning
Yamaha DS7, RD250, RD400, Yapol TZ250B, Daspa TZ350, TZ250A, FZ750/1000, Honda RS125, Jackson Special 250, Höpfner-TD3, Hejira TM250, Siroko TZ250, Tomic 200, Bakker TZ350B

Offline 5port

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Re: RD350 Track Bike build
« Reply #17 on: June 09, 2020, 12:50:13 PM »
Hi Uwe, good to see you!  There maybe a part from you later in this story. ;)
I am not certain about the slotted rods being standard on 2R8, is it possible that they changed during production runs as I have 2R8 cranks with plain rods? I will look.
Yes, if you have the dry clutch parts etc you can use them.  :)
The Fahron tuned R5 cylinders will be interesting, piston porting so probably a bit fussy!  Cheers

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Offline german

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Re: RD350 Track Bike build
« Reply #18 on: June 09, 2020, 01:05:40 PM »
Hi Chris,
I am pretty sure that the bike will sit around more rather being used. So if the bike will be a little fussy it will be no problem, could not be more fussy as my TZ's....... I rode not more then 20 miles with a bike the last 8 years........ >:(
But now my shoulder/arm is pretty well again and it could be as least theoretical possible to ride :)
I will try to TÜV, the more restricted version of your MOT, the bike as well. It is a not easy task to do this as near every part you change on a bike in Germany have to be TÜV approved. But I have a frame where many entries of aftermarket parts are written in. Some are cary vague, so I am pretty free what I will use.
Wheels will be Astralites(which never had TÜV approval in Germany), alloy tank, TZ seat, rearsets, DG exhausts and so on.
If it fails the TÜV I always have the chance to ride the bike at our race meetings at the free trials or parades.
Regards Uwe

« Last Edit: June 09, 2020, 02:02:21 PM by german »
Classic Racers do not hide the ashes, they keep the fire burning
Yamaha DS7, RD250, RD400, Yapol TZ250B, Daspa TZ350, TZ250A, FZ750/1000, Honda RS125, Jackson Special 250, Höpfner-TD3, Hejira TM250, Siroko TZ250, Tomic 200, Bakker TZ350B

Offline Motty

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Re: RD350 Track Bike build
« Reply #19 on: June 09, 2020, 01:46:37 PM »
I have only just caught up with this thread Chris.
Thank you for documenting your build it looks like it should be an interesting one
Pass the popcorn Tony

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Offline 5port

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Re: RD350 Track Bike build
« Reply #20 on: June 11, 2020, 11:22:49 AM »
I will continue to expand on some of the details that are covered in the main progress because, I am aware that there are many minor points that do not come up as I cover the main bits.  :)
As I am also referring to TZ stuff and mix and match, I would like to avoid anyone getting their fingers burnt by following an expensive course of action or, buying parts that cannot work.  So, expect some more details!   :)  Cheers

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Offline 5port

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Re: RD350 Track Bike build
« Reply #21 on: June 11, 2020, 05:04:52 PM »
Back for some details!  :)



So, as I said, I think I can add some details that might help anyone with parts and TZ/RD interchangability.  I cannot go into everything as there are myriad details.  Also, if you want to build a real TZ, you will have to do a lot of research yourself to be happy with what you do because, not all the history is available to mortals.  :o   
A great info source is Greg Bennett's great book "Yamaha two stroke production roadracing motorcycles" vol 1.
So, I will start with the crankcases.
Generally, the TD3/TR3 and TZ250/350 up to the late 70's had cases with the same dimensions as the DS7, YR5 and the RD's.  The style and detail changes sort-of follow the road bike development but, there are loads of anomalies (like when the different side cases were changed to later styles-there are loads of variations even in Official Yamaha portraits) and, you will have to satisfy yourselves about that!  There was a big change around '76 model year when the cases changed and the clutch cable became attached to the left side case, rather than through that small square cut-out on the top of the main crankcase on earlier engines.   
The genuine TZ250/350 cases are rare because they got raced, crashed, repaired, rebuilt  and swopped about.  So, there is no doubt that RD cases can be modified and substituted, even on gen TZ's.  The engine numbers usually did originally match the frame  in the same way as the RD but, they are often different today or, remarked.
The engine id code can help.  Overall, in this period the engines on the racebikes stuck with "DS7"  for the TD3/TZ250's and "R5" for the TR3/TZ350.  The next 6 numbers start with 99 followed by 0 for '72 and 1 for '73 etc...probably!   ???  The usual Yamaha system of reserving the first 100 numbers for development bikes seems to apply.  So, the first production TD3 engine (for '72) would have been DS7-990101.  The first TZ250 engine for '73, DS7-991101.  Now, these numbers are not cast in stone but, any DS7-99---- or R5-99---- cases are worth checking out.  Of course, cases can have been remarked or replaced so, the numbers on their own are not full provenance. Buyer-beware.
Yamaha had different dies for the TZ castings, you can tell because there is no small gbox oil transfer hole below the gearshifter cam mounting on the dry-clutch crankcase. Also, the TZ crankcases continued to have the steel crank bearing mount inserts fitted, though I don't know if or when they reverted to the all-alloy construction like the RD?   I would not be surprised if the bare castings were machined and processed on part of the RD production line as the fit and finish is very much identical to the roadbikes.  However, the racebikes do have the extra crank "C" ring grooves, the front mountings bored out for the rubber mounts and the gbox oil drain point is drilled and tapped in the centre of the case, unlike the RD which is tapped in the boss further to the right.
Now most of that is only important to a TZ owner/builder.  However, it does show that the RD cases are good for TZ conversions and, shows you just how close they are!  :)

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« Last Edit: June 15, 2020, 08:49:25 AM by 5port »
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Offline tony2stroke

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Re: RD350 Track Bike build
« Reply #22 on: June 11, 2020, 05:38:36 PM »
I do love to know details, I am a very curious gezzer, better than looking in a manual  :)

Offline 5port

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Re: RD350 Track Bike build
« Reply #23 on: June 12, 2020, 12:01:31 PM »
OK!  Some more details.  :)



Lets look at some gearbox details.  Some of the gbox info is badly covered in the manuals and, this is the best that I have.  ;)
The 6-Speed shifter mechanism of the '72 GP racing TD3/TR3 (the 328 model type)  was then used on the TZ250/350 racebikes from introduction in '73 through to the end of the '70s.  Amazingly, virtually the same shifter and gbox layout was then fitted to the new RD250/350 range in 1973.  Definitely "Race Developed"!   The shifter parts are almost all the same, with only minor changes for the RD and the differences are: the Cam drum (same, but no neutral light contact on race bike), stopper plate (race bike plate same but has very shallow Neutral detent), Detent plunger (is a ball on racebikes) and that is it, just gear lever shiftshafts on some racebikes were two ended and detent plunger housing is different.  So, a racebike gbox gearset will work in an RD shifter mechanism and vice-versa, just those minor differences, the main one being the neutral detent is very weak on the race gbox so that changes between 1st and 2nd  slip through with less chance of neutral.  :)
Now the gears and shafts.  These are completely different.  The dry clutch makes the race input shaft longer and the output shaft uses two collets to locate the gear at the sprocket end of the race output shaft.  That said, the shafts and gears can fit in either sets of cases and, they use the same bearings.  Of course, the race gbox ratios are closer than the RD's and, the race 1st gear is  high, almost 2nd on the RD gbox.  That said, the later RD (521 type) gearset that came in with the Eu 250/350B and then was further updated in the new RD250/400 range in '76, is quite close ratio and, works well for many track bikes.  The race gears have undercut dogs to help engagement but a good condition RD gbox works fine.  The condition of components is important for any gbox so, careful inspection for:  pitted teeth, overheating (discolouration), cracks and worn or rounded engagement dogs is important.  The only guidance I know from Yamaha about shimming the gears I will cover now.  The RD gbox comes standard with just the single shim on the drive end of each shaft.  The RD spinning gears are retained with circlips and a special washer-no shims as such.  The racebike is the same but Yamaha guidance is that the spinning gears should have an axial clearance of 3 to 5 thou inch and, that is set with shims, between the circlip and the special washer A/R, to bias the spinning gear towards the engagement dogs that engage with it.  ;)  I have not got the experience with this shimming to tell you the difference but, I am tempted to try on the RD "E" gbox that I am using on my trackbike.  Certainly, the spinning gears on RD gboxes seem to have more than 5thou inch axial play on the spinning gears.  ???
Lastly for this, the racebike gearshafts in this period kept the finely splined ends for the clutch and sprocket.
 Overall, you can now see that the later RD gbox is a fairly good basis on a trackbike.  Some classic RD racers use a dry clutch with the RD gbox and for that it is possible to get a special clutch shaft that is longer to suit the dry clutch fit.  Remember though, this is just a general talk through the main differences.  ;)  Cheers

5port

   

 
         
« Last Edit: June 15, 2020, 08:57:10 AM by 5port »
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Offline tony2stroke

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Re: RD350 Track Bike build
« Reply #24 on: June 12, 2020, 02:00:21 PM »
And a great talk through it is  :)

Offline 5port

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Re: RD350 Track Bike build
« Reply #25 on: June 13, 2020, 04:32:30 PM »
OK, back to the gbox shimming topic.  I have checked the output shaft of my RD250 gbox and found that the spinning gear nearest the sprocket has 12thou inch side to side play and, the other spinning gear in the middle-ish has 15thou inch.  So, that would seem to mean I am miles greater than the Yamaha advice of 5thou inch max!  :'(

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Offline Motty

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Re: RD350 Track Bike build
« Reply #26 on: June 13, 2020, 06:38:20 PM »
0.005" is a tight tolerance!
Do you have a box of spare shims, or are they now on the shopping list?

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Offline 5port

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Re: RD350 Track Bike build
« Reply #27 on: June 13, 2020, 07:23:18 PM »
0.005" is a tight tolerance!
Do you have a box of spare shims, or are they now on the shopping list?


Well, I think it is an optimum setting for best operation and minimum tendency to jump out of gear in racing conditions.  These shims do not appear in the parts list for the RD or the racebikes and I do not think that they were shimmed at the factory. ???  I suspect that this is a racing "tuning" thing.  So, I am going to do it on my trackbike.  I spoke to Gordon Jones and he advises it.  I will get the shims from him.  :)

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Offline G Jones

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Re: RD350 Track Bike build
« Reply #28 on: June 18, 2020, 10:23:06 PM »
These shims do not appear in the parts list for the RD or the racebikes and I do not think that they were shimmed at the factory. ???  I suspect that this is a racing "tuning" thing.  So, I am going to do it on my trackbike.  I spoke to Gordon Jones and he advises it.  I will get the shims from him.  :)
5port
The 25mm shims are listed on the parts list I use - although the numbers are arse about face - Part numbers 46 & 47 are reversed. (I marked all the errors I have found)
I had a new batch of shims recently - I now have a couple of in between sizes - although I've yet to decide how many of which thickness and put them into a usable kit - was it you that phoned me last week ?

Offline 5port

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Re: RD350 Track Bike build
« Reply #29 on: June 19, 2020, 08:25:20 AM »
Hi Gordon, Yes, I am after the shims.  :)
As far as the shims in the "parts book", they are an early 156 part number but, they are not in the TZ250A/350A Yamaha owners service manual Jan 1974, not in the Yamaha parts lists for the early TZ  and I never found a reference to them in any RD manual.  I see that the shims 46/47 do appear in the '76 TZ250/350 C parts list.  I wonder if they were used in the TD3/TR3 with the same gbox originally or, were they introduced on production TZ's in '76?  Funny but, that '74  TZ service manual says nothing about the gbox overhaul, it just refers to procedures in the RD service manual.  Cheers

5port     
« Last Edit: June 19, 2020, 03:09:45 PM by 5port »
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