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Messages - Momus

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Suzuki / Re: 1978-onwards RM/PE250 lower fork yokes
« on: March 19, 2018, 10:47:28 PM »
In my experience the press fit of the stem into the triple is very tight and heating is required or you risk bending. Ditto when replacing.

General Discussion / Re: What ever happened to event promotions?
« on: March 15, 2018, 04:07:15 AM »
They don’t think that at all. They know there are no participants on the forum.
A bit cynical Ted. The lack of photos is a better reason.

Tech Talk / Re: Betor fork sticking
« on: February 19, 2018, 04:09:00 PM »
G'day, I have a set of Betor forks from a Bultaco MK7 125 in which one of the fork tubes sticks at the lower end of the tubes stroke. It only happens to the non brake arm side slider. I have stripped and cleaned them and replaced the seals and it still does it, just not as bad. Have tired the tube in the other slider and it moves through the full length of the stroke nicely. Any ideas on a fix would be greatly appreciated.

Probably dinted; you might need to get in the slider with a wheel cylinder hone.

Maico / Re: 1974 maico
« on: February 10, 2018, 02:27:22 PM »
I remember reading about the white/black/silver scheme in a Maico restoration story written by Terry Good the US works bike collector.
Sounded unlikely for the factory to go to pointless trouble with multiple coats so I assumed it was because that particular bike had a frame color history.

Tech Talk / Re: Need help with 240 volt tig welder selection please
« on: February 07, 2018, 09:06:20 AM »
I started alloy tig welding about 40 years ago using one of these.
Add says 150 amp but they are actually 200 amp, a few years after buying my first one I got a second and joined them together and had a 400 amp AC high frequency welder.
They were in service doing repairs on mainly Harley engine cases and heads up until about 5 years ago when I picked up a new 350 amp inverter machine that was made in China and it has worked well in that time.
I stopped doing the Harley shit just after buying the new welder as I just got sick of welding and dealing with the shops.

 A good 200 amp welder sounds like it will do all you want but the foot pedal are really only good if you can sit at a welding table, I have one with the new welder but hardly use it.
Someone was talking about filler rod earlier. You will need atleast 3 types if you are to play with bike stuff. I mainly use 5% silicon on cases as it is the lowest melting point, the 5% mag is the strongest and machines better but is more prone to cracking on cooling, pure magnesium also comes in handy but it is expensive and hard to get.
With the Gas. Boc do a deal with the D size[small] bottles where you pay $108 rental a year and get 1 free fill of gas a year. Bunning have it now as well with a $200 refundable deposit on the cylinder and no rental. I still pay the $240 year rental on the E size argon as I go through a bit and it is about half the price for the gas in the big bottles.

Good luck and do plenty of practise before doing your big fin head.

Valuable! thanks Sleepy 8)
Your not going to believe this,,, I have one of those EMF "pilot Arcs" buried in the shed,,, did a lot of steel etc with it in the day, then bought it of my employer when we decommissioned the site. Still no 415v power at home though ::) ::) ::) ::) see if I can get close enough for a pic,,,

Started with an EMF as well. Great pie warmers.

Honda / Re: Honda XR 200 stuff for sale
« on: January 24, 2018, 03:18:27 AM »
Where are you?

Tech Talk / Re: Fork leg straightening
« on: January 16, 2018, 07:45:14 PM »
A straight edge and eyeball is all that is required to check the stanchion.

Tech Talk / Re: Fork leg straightening
« on: January 15, 2018, 11:28:49 PM »
Look for the rub witness and hone the leg with a brake cylinder hone if only slight. Other method would involve sliding the leg over the straight stanchion and heating to relieve it.

Tech Talk / Re: Measurements for side-bleed expansion chamber?
« on: January 13, 2018, 02:25:40 AM »
On the practical side old steel bicycle frames are a good source of relatively thin wall tube for this sort of work.

Tech Talk / Re: Fork leg straightening
« on: January 13, 2018, 02:23:04 AM »
Ian at Detroit Flame Hardening in Moorabbin straightens steel axles after heat treating; he may do your stanchion.

Tech Talk / Re: Measurements for side-bleed expansion chamber?
« on: December 22, 2017, 09:05:28 PM »
I cant see that there could be much (any?) difference between a “side bleed” and an “internal stinger” that starts where the side bleed would exit. (You could even bend the stinger so the entry was near the edge of the chamber, where the entry to the side bleed would be) Externally, the second option looks standard, just an apparently short stinger (some hidden in the chamber)
Yes, there shouldn't be much difference, but I suppose it depends on whether one wants the silencer to stay in the same place. If so, the "internal stinger" arrangement provides an extra length of tube which is nearly straight (and hence as short as possible), while for the "side bleed" arrangement, the extra length of tube cannot be anywhere near straight (so must be longer)...although I wonder whether this admittedly small difference in extra length would have any detrimental effect :-\ .

I should point out so far that I am satisfied that both "internal stinger" and "side bleed" designs should provide significant noise reduction with little or no effect on performance. The only question which remains is the necessity (or not) of increasing the diameter of the stinger to compensate for the increased length (in order that the cylinder does not retain any significant extra heat).

A suggestion has been made to me for converting an existing "normal" pipe design (with 25.4mm ID stinger, about 380mm long) to the "internal stinger" arrangement, whereby the internal portion of the stinger would be made from 28.6mm ID tube (about 250mm long), but the external portion would still be 25.4mm ID and retain its usual length. As I lack expertise in this area, I must ask the following questions:
a) Would the proposed increase in length require an increase in stinger diameter to prevent excessive heat retention in the cylinder?
b) If so, will the suggested stepped design achieve that objective?
c) If an increase in stinger diameter is required, is it better to make the stinger of uniform ID throughout, rather than the suggested stepped design?

AG Bell offers some handy advice about stinger lengths and IDs in his book (120-280mm long and 26-28mm ID for a 250cc cylinder), but these measurements must only apply to "normal" stinger arrangements because he makes no mention at all of any alternative stinger design. A brief look through one of my other two-stroke tuning books (JC Dixon) revealed some info on both "internal stinger" and "side bleed" arrangements, but annoyingly no advice is given about length or diameter (other than to effectively state that diameter is very important and length is not so important).
Jennings' recommendation for stingers states diameter to be 58-62% of lead-in (header?) pipe diameter and length to be twelve times whatever the stinger diameter is. In my case, the ID of the stub manifold at the cylinder is 44mm, giving a stinger diameter of 25.5-27.3mm and a (nominal) length range of 300-330mm. Of course, Jennings' experiments with internal stingers were carried out while keeping the stinger length constant - only its position was varied.

This comment over on the Penton board may give some leads...

"...Ollie McKagen built some wild pipes. He also designed and fabbed some wild and crazy suspension concepts. He was the smartest/most "out there" guy I ever met...I saw him weld pipes with the "internal stinger". He was extra diligent to ensure the backflow went into the center of the pipe to provide bottom end grunt. He wrote some articles for Dirt Bike or Dirt Rider. He patented several items too. There is some info on him on the Eurospares website...
Thanks for the reference. I have had a look at the Eurospares web-site, but it only deals with Ollie's suspension arrangements (all the bikes in the photos are four-strokes). A few brief Google searches did not reveal any results relating to his internal-stinger pipes, but there were a few more results relating to his suspension arrangements - most particularly his "funny front ends".

Unfortunately I ran out of expertise on this topic a long time ago :( . Also I have to go and lie head hurts :-[ . Further contributions from anyone knowledgeable, experienced and/or interested are welcome!

Thanks & regards,
No one knows the answers James. Make your chamber with a flange, gland or spigot at the end of the baffle cone and test variations. If you do this thoroughly you will probably be the world expert on this sort of empirical testing on your model engine.

Yamaha / Re: YZ125K Rebuild
« on: November 23, 2017, 08:47:22 PM »
I'll have a look tonight Lozza.

Stator: 1442    54/A/18
Coil:    105458
Rotor:  940 - with a 3/4" bore from the B50 crank.

Yamaha / Re: YZ125K Rebuild
« on: November 23, 2017, 02:52:36 AM »
I'm going through something similar having been given a PVL analogue ignition supposedly to run a 500cc 4 stroke single, that when correctly i'd, was an 1800 windings 2 stroke unit for a kart.
PVL's site says, at least in regard to the analog systems " the approval of an ignition coil/stator unit combination must be registered by PVL. We urgently discourage random combinations with a view to obtaining a different ignition curve, as we do not know if the electronic components are compatible..."

I've fitted a couple of smaller PWK's and found same deal with slow running and pilot passages. Also found that the seal of the jet block and the passage alignment might need a blueprint. These were OKO branded units.
Those will be the Chinese rip off Okos, saw a thread on how to pick them. Real Okos have Taiwanese flag on box is first clue, next is jets actually have markings
Have been running a real Oko for years on my Sherco & it's as good if not better than a Keihin PWK
Yes the OKO carbies with provenance are good and the cheapies easy enough to get right. I am using the sub 30 mm size which are very compact and ideal for smaller 4 stroke fitups. Benchmark for these though is the Keihin FACE.

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