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Topics - tony27

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1
CZ / 360 sidepipe pistons
« on: June 23, 2018, 02:36:00 PM »
Are pistons available for 360s? I know OTZ has rings in 80, 80.25, 80.5 & 80.75 but don't show 360 pistons
Any possible sources that people can suggest?
Not sure what size bore the bike I have coming is but if possible I would prefer to keep it as a 360 rather than open it out to 380 when I rebuild the engine

2
Tech Talk / Unlocking a motor
« on: June 23, 2018, 02:28:35 PM »
I have a CZ sidepipe coming which I've been told is locked up, has been sitting a long time so I don't know exactly how bad but knowing CZ bearings I assume rings stuck to the cylinder is the most likely reason
What is the best product to soak the cylinder in to slowly work on freeing things up?
Once the cylinder is free I'll be replacing every bearing in the motor, depending on condition of the bore I may get away with rings for a 360 which are available unlike I suspect pistons

3
Twinshock Trials / Longterm TY250C
« on: June 17, 2018, 07:00:35 PM »
Finally got my 250C back in a ridable state. We worked out it had been about 5 years since I'd ridden it last when the main bearings & rings were that worn that the motor could be turned over by hand by gripping the end of the crankshaft with the flywheel off



While the motor got a full rebuild with the cylinder being bored to 1st oversize I made a few changes both to looks of the motor & had the swingarm extended with shedworks axle plates
The axle plates extend the swingarm by 38mm or so which puts a bit more weight to the front. As it turns out even with the lengthened swingarm the wheelbase is standard which confirmed that the steering head angle had been modified, the welds are far better than normal & the front down tube are completely smooth. We stood the bike in front of a Beta Techno & the fork angle is the same which makes sense as the Techno was the current bike when the mods would have been done
The original shock mounts were deleted & a gusset fitted to help strengthen the tubes above the repositioned mounts that were done before it's last ride
I fitted a DT250C head that Ian Cameron supplied me for looks, I race a 73 CZ & owned a YZ465H when I built the motor so radial heads are my preference. The combustion chamber is meant to measure the same. There was minor grinding of a couple of fins to clear the exhaust & I cut about 10mm from the rear to match it to the cylinder
An electrexworld ignition is fitted now with the band removed from the flywheel, I had to put marks on the flywheel & stator plate for timing while the head was off. Unfortunately we didn't get a chance to strobe the timing as per the fitting instructions & had to run it set at the middle of the slots but it seems to work well

I'll see what other detail photos I have & try to put them up at some stage

4
Tech Talk / Sloppy 34mm forks
« on: October 29, 2017, 07:32:06 PM »
I need to fit bushes to the top of my TY250 forks as both legs blow seals & if I grip each leg with the wheel out there is definite play in them
Does anyone know of a 34mm fork that has bushes in the top of the sliders or am I going to need to custom make a pair with a fairly thin wall thickness?

5
eBay Finds / RM400 rod kit?
« on: March 15, 2017, 11:01:18 AM »
Saw this on trademe, seller not quite sure about fitment
Have a read of the listing & check measurements.
http://www.trademe.co.nz/motors/motorbikes/parts-for-sale/engine-components/auction-1280717750.htm

6
CZ / 400 Falta timing
« on: February 04, 2017, 02:22:59 PM »
I've just received a Falta head to go with my Southbay modded Falta cylinder & have come across a couple of different ignition timing figures
Some sources like the Clymer manual say all 380s/400s should be timed 3.4-3.6mm but I've also seen a spec sheet that listed the Faltas as 3.8-4.0mm
Compression on the Falta was listed as being higher than the earlier models
What sort of timing figure are people using in their Faltas?

7
Tech Talk / Port repair
« on: December 13, 2016, 05:18:03 AM »
I picked up a cylinder out of the states for my CZ a couple of  months ago which has the boost ports added to run a big DH reed valve which I already have
When I put the reed block & cylinder next to each other I found the the intakes had been opened out about 5mm on each side & are that amount wider than the reed block which definitely won't allow that amount of opening up to match
I'm considering having the ports welded up a bit as well as the gap between the manifold mount & next fin filled in as my modified Falta cylinder has then getting the mount machined flat & matching the port width & reed block to each other
What are peoples thoughts on this or any other suggestions
 
The extra width is quite obvious here & you can see the gap I'm going to have filled in

8
Spaniards (Bultaco, Ossa, Montesa etc) / What year is this Bully?
« on: November 20, 2016, 05:25:08 PM »
Any idea what year & size this Bultaco is?

9
Tech Talk / Mikuni VM float height
« on: October 02, 2016, 10:15:22 AM »
What is a baseline setting for the float height on a new VM Mikuni?
I just bought a new 36mm to complete converting my CZ to reed valve & suspect the float height is a bit high, the overflow tube has a bit of fuel sitting in it & exiting corners the motor isn't running clean
I tried lowering the needle to the top clip which didn't really help & because I was running the motor in I couldn't bring myself to spend the time at higher revs to get around it
Really need to sort before I go back to work tomorrow night as the next meeting is on Saturday
 

10
Wanted / GEM V-6 reed
« on: August 15, 2016, 05:17:43 PM »
I'm after a G.E.M V-6 reed cage at the minimum, I haven't found the safe place that I put the reed cage & carb mounting block for my CZ while the exhaust port was being repaired
I still have the CZ specific main casting & can get another mounting plate machined & retap the threaded holes to metric sizing
The 75 GEM catalogue suggests that the reed cage is common to multiple fitments with the main casting being the difference

11
Manuals & Technical Doco / 1975 G.E.M catalogue
« on: July 06, 2016, 01:44:06 PM »

12
Tech Talk / Piston window radius
« on: June 27, 2016, 03:18:54 PM »
Finally got the holes & slot put into the back of my CZ piston to Charlie Richardson's provided sketch for running a reed valve & would like to know how big to make the radius around the holes as I've never had anything to do with modifying pistons
At the moment I've basically broken the sharp edge off both the inside & outside of the holes with needle files to .5-1 mm wide, is this enough to remove to the stresses from having sharp edges


Initial work 

13
CZ / Folding footpegs for side-piper
« on: June 22, 2016, 07:05:27 PM »
What do people do to get folding footpegs on their side-pipers?
I got rung up earlier tonight to find out if I'd like to race a 360 in pre70 this year instead of the husky 400 cross we'd been planning on.
I know I can get a new non folding set fairly easily to modify if needed but pointers on what others do would be helpful

14
Tech Talk / Boyesen reeds
« on: June 01, 2016, 11:55:26 PM »
Is there a cross reference for boyesen reeds with dimensions available anywhere, have a couple of aftermarket pre75 reed blocks that I'd like to see there are off the shelf reeds that fit

15
Husqvarna / 69 400 Cross
« on: April 23, 2016, 09:57:43 PM »
I got offered a 69 400 Cross to use in pre70 next season today, are there any downfalls with them ie known weak points or parts that are impossible to get?
How different will I find it to ride compared to my 73 CZ?

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