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Messages - James P

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1
I would like to resurrect this topic in the hope of getting some advice. For the purpose of the exercise, I would like to differentiate between two different arrangements which effectively achieve the same objective (i.e. noise reduction):

1. The "side bleed" arrangement, where the stinger emerges at an approximate right angle from the parallel-wall belly section of the expansion chamber

2. The "internal stinger" arrangement where the expansion chamber resembles the traditional type, but the stinger starts in the parallel-wall belly section and continues through the reverse cone before emerging in the usual position at the end


I have had some experience with Arrangement No.1, mainly because it suited that particular bike to have the silencer mounted below the reverse cone portion of the expansion chamber - I had to keep the chamber as short as reasonably possible. This arrangement was a success in that it kept noise at a reasonable level. The pipe was built from scratch (using a pair of pressings for the diffuser, belly and reverse cone sections), so I can't make a direct comparison with an otherwise identical pipe having a traditional "rear exit" stinger (i.e. no before & after results). However, I am satisfied with performance, so have left it there.

Moving on to my present project; I want to quieten the exhaust on my PE250B (see here for some background info: http://forum.ozvmx.com/index.php?topic=42480.0). Using Arrangement No.1 (the "side bleed" set-up) would be difficult, as there isn't much space to accommodate the existing FMF silencer (which I want to keep) in any position other than at the end of the stinger in the traditional position. The existing stinger is reasonably long (about 380mm from end of reverse cone to start of silencer), although it could be shortened slightly (perhaps 30mm) without the silencer fouling the left-hand side cover.

Gordon Jennings recommended that for the "internal stinger" arrangement (No.2 listed above), the stinger entry should be located "an inch or so" before the start of the reverse cone for optimum results (i.e. noise reduction with no performance loss). This would add about 250mm to the length of the existing stinger.

Since I have some other specialist jobs waiting to be done (including magnesium welding and removing dents from existing chambers), I approached a well-known service provider (and member of this forum) who carries out such work and also builds expansion chambers. He is willing to either modify my existing chamber with an internal stinger or to build a new chamber from scratch incorporating the same feature. I initially intended to have the existing chamber modified, but due to certain difficulties I am now leaning towards having an entirely new pipe made. However, he has never made an "internal stinger" chamber before and would like me to specify some particular requirements for the proposed pipe.

With that in mind, there are a few questions I have for those who can offer the benefit of their experience:

a) Using the dimensions of the existing chamber as an example; If the existing 25mm ID stinger is already 380mm long (with allowance to shorten by 20-30mm), would an increase in diameter be required (to prevent undue heat accumulation in the cylinder) if another 250mm length is added?

b) For structural integrity over a long period of time, should the internal end of the stinger be welded to the wall of the parallel-wall belly section and/or the reverse cone section? If so, is this accomplished simply by drilling a hole (or holes) and welding through it/them as part of the assembly process?

c) Although Gordon Jennings didn't mention it, is it advisable to alter any other aspect of the design of the chamber to allow for the internal stinger?


As an alternative, there may be enough space on the bike to allow for a "side bleed" stinger, turning a right angle, then meeting up with the "existing" stinger in the normal position (meaning that the reverse cone would have a closed end), but this would add even more length, which may be undesirable from a heat retention point of view.

I'd be glad of any advice or useful opinions 8) .


Thanks & regards,
James

 

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Suzuki / Re: Suzuki PE250B
« on: December 06, 2017, 04:08:31 PM »
Thread used by Yamaha is M16x1.5 right hand thread, tap itself is left hand thread

Thanks for the info Tony. Looks like Yamaha used the same arrangement, but different thread :( .

I think I will order the 44300-05115 fuel tap and carry out some flow tests. I'll post the results when it (eventually ::) ) happens...

Regards,
James

3
General Discussion / Re: Another new friggin tax
« on: December 04, 2017, 10:59:25 PM »
I wondered how this container return scheme was supposed to work Zane - your report is not good news :( . However, I was under the impression that the Government was to receive the "tax" from the drink companies on the sale of each container - the signs I have seen in the supermarket imply that this is the case, although no doubt some of the money will go towards establishing and running the collection centres. They are obviously banking on the likelihood that people won't bother to take the containers to a collection centre to claim their money back - what you say seems to confirm that it will be as inconvenient as possible >:( . Another windfall for the Government...
If the actual return of containers is to be processed "electronically", there's absolutely no chance of anything going wrong there...is there ::) ? Like you, I can't see how this new scheme will make much difference to the litter situation. Anyone had any experience returning containers for a refund yet?

Regards,
James

4
Wanted / Re: RM125, 250 or 400 fork yoke set...
« on: December 04, 2017, 10:34:34 PM »
I have a set if you still need them $100 plus post.
cheers don

Thanks for your offer Don - PM sent.

Regards,
James

5
Kawasaki / Re: KLX250 fork yoke dimensions...?
« on: December 04, 2017, 10:52:45 AM »
...if you need the handlebars out of the way of the fork tubes have you looked at offset handlebar clamps ?

Pokey posted a photo and link to such clamps here http://forum.ozvmx.com/index.php?topic=42482.0. These clamps are certainly an option, but I'd prefer the end result to look both "standard" and "period", by using OEM parts from the same era (although much later yokes may not necessarily look too modern). Thanks for the suggestion though - I'm keeping this option as Plan C ;D .

Regards,
James

6
Suzuki / Re: Suzuki PE250B
« on: December 01, 2017, 11:23:35 PM »
http://forum.ozvmx.com/index.php?topic=40919.0
Hey James
The above link is a thread for an new aftermarket petcock to suit your model. Unfortunately there is no reserve but if you would like it I can post it to you no charge.
Thanks for the offer :) . I have the genuine fuel tap fitted at the moment, which does the job well enough (just without a reserve function :( ). I am tentatively planning to buy the 44300-05115 tap and measure the fuel flow (for both "normal" and "reserve" functions) - if it is sufficient I will use it as is...if not, I will investigate modifying the tap to improve the flow.
If for any reason I need a pattern fuel tap like the one you now have spare, I'll be in touch!

Thanks again & regards,
James

7
Kawasaki / Re: KLX 250 Lighting coil - Is there a way to upgrade it?
« on: December 01, 2017, 09:04:10 PM »
Steve at Betta Bikes rewound my Suzuki PE250B stator lighting coils (normally two separate 6V coils; one for stop light, one for everything else) to make them identical and they are now connected in series for a single-wire 12V output. Steve claims 60W output for this set-up. The lighting system is now 12V AC (no battery), but I do have a regulator connected to make sure the voltage doesn't get too high.
I daresay you could obtain a similar service elsewhere, but I generally prefer to use people with bike-related experience.

Regards,
James

8
Kawasaki / Re: KLX250 fork yoke dimensions...?
« on: December 01, 2017, 08:45:34 PM »
Not KLX, but I had a look at some KLR250 (1989 I think) yokes today. The distance between fork centres seems to be 185mm, while the offset is somewhere in the region of 25mm (yokes still on bike, so accurate measurements difficult :-[ ). The important dimensions thus seem similar to the Yamaha IT (1977-1980) yokes which I also know about. Not absolutely ideal for my purpose but could be adapted, so the IT or KLR yokes will be my back-up option if I can't get the RM ones I want.

Regards,
James

9
Yamaha / Re: Dimensions of yokes for Yamahas with 36mm forks...?
« on: November 30, 2017, 04:40:32 PM »
The 60mm offset ones are from the inline axle forks. The leading axle TT/XT500 clamps will have  a lot less offset than 60mm.

Ah yes - I forgot about the difference in axle orientation. Some basic research suggests that the change to leading axle occurred in 1979 for the TT500 and in 1980 for the XT500.
It seems that the 1979-onwards (at least until 1981) TT500 used the same top yoke as the 1977-1980 IT175/250/400/425 (for which I have the dimensions), while the 1980-onwards XT500 used a top yoke which positions the handlebars almost directly above the fork legs (hence preventing the fork legs from being pushed very far through the yoke).
The IT/TT yokes are a possibility, but would require other modifications which I'd like to avoid if possible. There could be other Yamahas with yokes suitable for my purpose, so if anyone knows the details, please let me know!

Thanks & regards,
James

10
Wanted / Re: RM125, 250 or 400 fork yoke set...
« on: November 30, 2017, 04:15:42 PM »
Thanks for looking K. The later 36mm yoke with fixed laid-back handlebar mounts may be of use - do you know what bike it originally came from? If possible, could you please measure the following dimensions:

a) the distance between fork centres
b) the offset (the perpendicular distance from the centre of the steering column to a straight line between the fork centres)
c) the inside diameter of the hole for the steering column

Does this later 36mm top yoke have a matching bottom yoke (with or without steering column)?

I am following up a number of leads at this stage (with varying amounts of promise), but nothing is definite so far. Therefore, any assistance will be gratefully received 8) .

Thanks again & regards,
James

11
Suzuki / Re: Suzuki PE250B
« on: November 29, 2017, 08:33:28 PM »
Tony,

The PE250B tap has a threaded nut which engages with a male thread (spigot) on the tank. From memory, the thread on the tap is left-handed (Lambrettas are like that too) to allow proper adjustment and seating.

I did also find reference to two OMG taps with M14x1.5 thread:

01Z3254030
01Z3254190B

However, I think these both fit into a female thread in the tank, which presumably means the thread is "normal" right-handed.

I'd certainly be glad to know the details of the thread(s) on your CZ tap though...if only to rule it out as an option :( .

Thanks & regards,
James

12
Suzuki / Re: Suzuki PE250B
« on: November 29, 2017, 06:56:05 PM »
Yes i had considered this and even thought it may be an issue when i posted that info. I will have to find mine on the weekend. I know the tube is small. You wont find it easy to find something else that fits. I know the tube is small. Do you know the size of the hole of the stock tap on the inside? I got a feeling these OMG taps would flow more
http://www.omgitalia.com/en/fuel-taps-for-cross-enduro-trial-and-quad-bikes/

Have a look what is on this site. From memory the thread is M14 X 1.5 but its a bit of a guess. You will need to check..

Usually ebay UK/Europe sites have these OMG taps.

When I first got the PE, I thought the fuel tap fitting looked exactly like a Lambretta. However, the Lambretta tap is a little larger and the thread is M16x1.0 (you remember correctly - the PE thread is M14x1.5).
OMG was one of the makers for original Lambretta fuel taps and still makes them, including big-bore versions which flow at least 600ml per minute. Although this is a fairly arbitrary figure, I tend to use it as a starting point for checking fuel flow capability for 175-250cc single-cylinder engines. Although I may accept a tap which flows less than this amount, I would prefer it not be too much less.

I seem to remember investigating OMG when I first built the PE, but the lack of correct thread size meant it was a non-starter. I suppose a special nut could be made to adapt an OMG or other brand tap to the PE tank, but it would probably cost as much as the tap itself!
Unfortunately I haven't got a spare standard PE tap to check measurements etc., but I am wondering whether it is possible to bore out the passages in the 44300-05115 tap to improve flow. The outlet looks to be about 5mm ID (which should be adequate), so it should just be the internal passages and valve which need modifying, along with fitting a larger ID brass tube. However, this involves a bit of faffing about and it would likely be necessary to obtain larger filters to prevent debris in the tank from blocking the passages over time.

Although a quick bit of research shows that mid 1970s TS250s used fuel taps which were shared by some 50cc and 100cc models (as for the 44300-05115 tap), I have no idea of the sizes of the internal passages. Anyone who knows of a more suitable out-of-the-box fuel tap with a reserve function to fit the PE250B fuel tank, please let us know! In the meantime, I will continue the research... :-\

Regards,
James

13
Yamaha / Re: Dimensions of yokes for Yamahas with 36mm forks...?
« on: November 29, 2017, 06:03:41 PM »
OK - thanks very much Mick. It seems that the XT/TT yokes make the fork centres a little wider than I really wanted. That in itself is not really a problem, but the offset is about double what I wanted. Nevertheless, thanks for taking the trouble to measure 8) .

Regards,
James

14
Wanted / Re: RM125, 250 or 400 fork yoke set...
« on: November 28, 2017, 09:30:27 PM »
Thanks K (& L for the photos!) - I'll await your further advice.

Regards,
James

15
Yamaha / Re: Dimensions of yokes for Yamahas with 36mm forks...?
« on: November 28, 2017, 09:28:44 PM »
Thanks for that info Mick. Are the fork leg holes in the top yoke 35mm...or something else?

Whatever the case, can you easily measure the distance between fork leg centres and also the offset for the XT/TT yokes (I gather they are the same :-\ )? Oh, and the ID of the hole for the steering column too :) .

It appears so far that 1978 RM125/400 (or 1978.5 RM250) yokes are my best bet, but I've still got to find some! Until then, any further info on Yamaha parts would be most welcome.

Thanks again & regards,
James

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