Gasket tickness

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Re: Gasket tickness

Postby FM350 » Thu Sep 29, 2011 6:56 am

[quote="FM350"]The old TY250 twinshock motor is a little gutless, and the main reason for removing the flywheel weight is to give them a bit more get up and go, which makes the bikes easier to ride in modern type sections, which are often a lot tighter than those common in the 1970s. Better still though is to fit better intake and exhaust systems, do some alterations to the porting and squish clearance, which will greatly improve running, to the extent you can then fit a heavier flywheel weight.

Easy and cheap way to improve the exhaust, is to fit back box from something like a YZ125, which can often be found used on Ebay, and will fit many bikes after a few simple alterations. The TY front boxes are very restrictive though (as are the WES replacements!), and making something suitable seems the only way to go here.
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Re: Gasket tickness

Postby Jon V8 » Sun Oct 02, 2011 3:18 am

FM350 wrote:
FM350 wrote:The old TY250 twinshock motor is a little gutless, and the main reason for removing the flywheel weight is to give them a bit more get up and go, which makes the bikes easier to ride in modern type sections, which are often a lot tighter than those common in the 1970s. Better still though is to fit better intake and exhaust systems, do some alterations to the porting and squish clearance, which will greatly improve running, to the extent you can then fit a heavier flywheel weight.

Easy and cheap way to improve the exhaust, is to fit back box from something like a YZ125, which can often be found used on Ebay, and will fit many bikes after a few simple alterations. The TY front boxes are very restrictive though (as are the WES replacements!), and making something suitable seems the only way to go here.

We have recently had this conversation on TC about TY250's being gutless - I made the case for the other side,both of the Ty250D's I have run well and dont lack power,both have standard carbs,but my main bike has a WES exhaust on it.removing the flywheel weight makes them pick up quicker,but as said much too easy to stall.I put mine back on after I started riding my HT5 Ariel.(Which is ridden just on the throttle hoverever tight the section,the clutch is left well alone)Getting back on the Yam and trying to leave the clutch alone has resulted in me becoming a far better rider as this years results have shown.
As for the carb,there is simply nothing wrong with the standard one,keeping it clean is all it needs.
As I said on TC, most trials riders "think" they need more snappy power,but in truth for twinshock/classic events standard engines are fine - they just need to be in good condition,properly set up and maintained.Being able to trust an engine to do the same thing each time you roll the throttle open or closed is all you need.The number of riders I see fighting with immaculate bikes that are clearly running badly makes me wonder.They have obviously spent the money on all the trick bits but have no idea how to tune the motor.......
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Re: Gasket tickness

Postby Guy53 » Sun Oct 02, 2011 7:45 am

Jon V8, you are partialy right. First if the sections in trial we have to ride ( here in Canada ) were like the section were in the 70's and not setup for late 80's to mid 90's bikes it would help, and if the suspension' s( tire and shock ) would be as they were in the 70' where you would spin the rear wheel in 3rd gear on a flat rock I would totaly agree with you but it is not the case anymore. I don't say it is for the better, but it is what we have to ride, when the guy that is in front of you ride a SWM 350 and the one beind is on a M199 Sherpa you realy feel like a bit of Red Bull would help your TY 434. You are right in saying that a well tune moto is a far better companion in a section than a nice looking one.
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Re: Gasket tickness

Postby JC1 » Sun Oct 02, 2011 8:24 am

FM350 - what do you suggest would be "something suitable" for the front box?

Likewise for "some alterations to the porting" ?
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Re: Gasket tickness

Postby FM350 » Sun Oct 02, 2011 8:55 am

JC1 wrote:FM350 - what do you suggest would be "something suitable" for the front box?

Likewise for "some alterations to the porting" ?


The stock TY exhaust system is very restrictive, and the WES ones while they are lighter are almost as restrictive as the stock parts, and appear to be dimensionally similar to those made for the TY175.

Its possible to make a front box reasonably easily, but you would need to find some very fine perforated sheet steel to making the silencer core, which would take up about 75% of the internal area of the pipe, which ideally needs to around double that of the stock/WES systems.

Firstly on any TY you need to adjust the squish clearance, before even thinking about porting of any kind. Once the squish is adjusted, and if you are able to sort out the intake and induction systems properly, raising the exhaust roof, widening the inlet, and seeing if you can improve the reed block/reeds at all, will add to the improvements resulting from properly working intake and exhaust.

However before even thinking doing all this work, I would suggest having a good ride on a TY175, which with a few simple alterations to the steering, and footrest position etc, is likely to work a fair bit better than the much more dated feeling TY250.
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Re: Gasket tickness

Postby Jon V8 » Mon Oct 03, 2011 4:38 am

FM350 wrote:
JC1 wrote:FM350 - what do you suggest would be "something suitable" for the front box?

Likewise for "some alterations to the porting" ?


The stock TY exhaust system is very restrictive, and the WES ones while they are lighter are almost as restrictive as the stock parts, and appear to be dimensionally similar to those made for the TY175.

Its possible to make a front box reasonably easily, but you would need to find some very fine perforated sheet steel to making the silencer core, which would take up about 75% of the internal area of the pipe, which ideally needs to around double that of the stock/WES systems.

Firstly on any TY you need to adjust the squish clearance, before even thinking about porting of any kind. Once the squish is adjusted, and if you are able to sort out the intake and induction systems properly, raising the exhaust roof, widening the inlet, and seeing if you can improve the reed block/reeds at all, will add to the improvements resulting from properly working intake and exhaust.

However before even thinking doing all this work, I would suggest having a good ride on a TY175, which with a few simple alterations to the steering, and footrest position etc, is likely to work a fair bit better than the much more dated feeling TY250.

Or you could just get on and ride it.......
Few,if any twinshock trials need anything like a trick bike,anyone who thinks different is kidding themselves.Individual rider skill and fitness is far more important.
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Re: Gasket tickness

Postby FM350 » Mon Oct 03, 2011 7:45 am

Nothing at all to stop anyone riding a heavy underpowered TY250 in totally standard form if they are happy with that! However the UK Sammy Miller Championship round held yesterday, was won by a very trick TY250 twinshock/mono, with another very special TY fitted with an ex works 340cc motor taking second place. So while a standard bike is fine for anyone wanting to ride very easy club level events, you are not likely to see them being used by any of the riders with a serious chance of winning higher level competitions.
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Re: Gasket tickness

Postby JC1 » Tue Oct 04, 2011 9:46 am

FM - you haven't answered the question about the front box. You claim that the TY & WES ones are very restrictive, but you give no substance to your claim. Are you claiming that the outlet is too small, the volume is too small, the header is too small, or what?
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Re: Gasket tickness

Postby FM350 » Thu Oct 06, 2011 6:24 am

The volume is too small, and the internals of the WES systems appear to be more suited to the TY125, possibly in an attempt to reduce noise and or make the bikes run smoother.

Any of the TYs run an awful lot better with a properly designed and made exhaust system, and very few people realise that the exhaust system on all old TS trials bikes was made primarily with the lowest possible cost in mind, with little or no attention being paid to whether or not they worked well.

A good example of this is the dreadful "clubfoot" exhaust systems fitted to various models of Bultaco............these are very heavy, get clogged up with oil/carbon very quickly, and do a pretty good job of restricting the potential of the motor to run well.
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Re: Gasket tickness

Postby Jon V8 » Thu Oct 06, 2011 10:07 pm

FM, I guess you mean this bike;
TY250.jpg

I really fail to see how this bike is accepted in the Sammy series,its just not in the spirit of twinshock trials.Chris Koch would most likely still win on a bog standard whatever.Using bikes like that just winds up other riders who use appropriate kit.
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Re: Gasket tickness

Postby David Lahey » Thu Oct 06, 2011 10:32 pm

I can't recognise one single part on that bike that originated from a TY250 twinshock
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Re: Gasket tickness

Postby Bully fanatic » Thu Oct 06, 2011 11:58 pm

What about the front mudflap David it looks like it could be of an early TY. :D :D . Graham.
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Re: Gasket tickness

Postby Guy53 » Fri Oct 07, 2011 1:41 am

I think David, that your mind is close, the colour of the Yamaha logo look the same as the 76 model , Hi Hi, seriously my point is not that we should all '' transform '' our TY's into whatever that bike is, but what's the problem with making the ride fun espacialy for a non championship seeker like me, by '' preparing '' our bike so it will be pleasant to ride, I'm not the kind of rider that take my bike out of the shed 10 min before a comp. I enjoy fussing aroun the thing ( but not on the look ) . Also, the more I think about the restricted exhaust the more I think your right. I know that you can '' calculate '' a pipe, it would be fun to have one calculated for a std TY 250.

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Re: Gasket tickness

Postby FM350 » Fri Oct 07, 2011 5:54 am

Jon V8 wrote:FM, I guess you mean this bike;
TY250.jpg

I really fail to see how this bike is accepted in the Sammy series,its just not in the spirit of twinshock trials.Chris Koch would most likely still win on a bog standard whatever.Using bikes like that just winds up other riders who use appropriate kit.



Chris's bike complies fully with the ACU rules relating to the TS class, which require that the frame was originally built as a TS, with no modified mono's allowed. Jon Bliss who built the bike contacted the ACU to confirm these details before he started on the project.

However in terms of function the almost stock 300 Fantic pictured behind Chris's bike is every bit as good, and probably better in events where power is an advantage.

Bikes that are genuinely not in the "spirit" of competing in classic trials, are the modern day British specials, which are ridden in the "P65" class, and are actually far superior to anything vaguely reassembling an authentic older machine, and certainly provide their riders with a big advantage.
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Re: Gasket tickness

Postby FM350 » Fri Oct 07, 2011 6:05 am

Guy53 wrote:I think David, that your mind is close, the colour of the Yamaha logo look the same as the 76 model , Hi Hi, seriously my point is not that we should all '' transform '' our TY's into whatever that bike is, but what's the problem with making the ride fun espacialy for a non championship seeker like me, by '' preparing '' our bike so it will be pleasant to ride, I'm not the kind of rider that take my bike out of the shed 10 min before a comp. I enjoy fussing aroun the thing ( but not on the look ) . Also, the more I think about the restricted exhaust the more I think your right. I know that you can '' calculate '' a pipe, it would be fun to have one calculated for a std TY 250.

Guy



To make a working front pipe for a TY you simply need to use as large a volume as you can fit in the available space, and design it so the front 75% of the pipe contains a passive silencing element, and the rear part is an empty area to allow gases to expand. Link this to something like a modified YZ125 back box, and you have an exhaust which will in conjunction with some changes to the intake system, and alterations to the porting and squish, totally transform the lack lustre stock TY250. In terms of the work involved though, if you can do it yourself the cost will be very little, as the only new parts needed will be a flat slide carb, a few gaskets, and material to make the exhaust.
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Re: Gasket tickness

Postby David Lahey » Fri Oct 07, 2011 7:34 am

FM350 wrote:Chris's bike complies fully with the ACU rules relating to the TS class, which require that the frame was originally built as a TS, with no modified mono's allowed. Jon Bliss who built the bike contacted the ACU to confirm these details before he started on the project.

Where some cunfusion enters the discussion is that while the UK ACU rules may allow for recent manufacture of a bike frame for Twinshock class, here in Australia, for Twinshock class there is a major items manufacturing date cutoff of 1987. I realise the motor and wheels on that Bliss bike are pre-87 but the frame is obviously not pre-87.
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Re: Gasket tickness

Postby Guy53 » Fri Oct 07, 2011 9:41 am

FM, what do you mean by passive silencing element, I don't think you are tinking '' stuffing '' like material. Please explain I am as bloqed as my TY pipe.

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Re: Gasket tickness

Postby FM350 » Fri Oct 07, 2011 5:31 pm

David Lahey wrote:
FM350 wrote:Chris's bike complies fully with the ACU rules relating to the TS class, which require that the frame was originally built as a TS, with no modified mono's allowed. Jon Bliss who built the bike contacted the ACU to confirm these details before he started on the project.

Where some cunfusion enters the discussion is that while the UK ACU rules may allow for recent manufacture of a bike frame for Twinshock class, here in Australia, for Twinshock class there is a major items manufacturing date cutoff of 1987. I realise the motor and wheels on that Bliss bike are pre-87 but the frame is obviously not pre-87.


Here in the UK you can buy brand new £2k twin-shock and "P65" frames, so I guess the ACU had to OK the use of recently made frames on older bikes? None of these is as good as the Jon Bliss TY frame though, and personally I feel that anything with major parts from a later period should run in a "specials" class.

Costs in the UK are already completely out of hand in the "P65" class, with people spending up to £10K on building Brit "Specials" which are allowed by organisers to run as "P65's". The same thing to starting to happen with twin-shock, with the appearance of £7k TY Yams, and cobbled up bitsa RS Honda's built with TLR parts.

In terms of competitiveness though a well built stock 240 or 200 Fantic is far better than the top dollar TY's or RS Honda's, so hopefully TS wont go down the pan in the same way as "P65" has here.
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Re: Gasket tickness

Postby FM350 » Fri Oct 07, 2011 5:37 pm

Guy53 wrote:FM, what do you mean by passive silencing element, I don't think you are tinking '' stuffing '' like material. Please explain I am as bloqed as my TY pipe.

Guy



Passive silencing is generally glass wool type packing around a perforated core, and active is an arrangement of steel tubes, baffles etc, which work by reversing flow of exhaust gases. Passive silencers work better for serious competition, but do tend to get clogged pretty quickly on TS bikes, as many owners still seem to insist on using too much oil in the petroil mix.
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Re: Gasket tickness

Postby Jon V8 » Fri Oct 07, 2011 11:14 pm

FM350 wrote:
David Lahey wrote:
FM350 wrote:Chris's bike complies fully with the ACU rules relating to the TS class, which require that the frame was originally built as a TS, with no modified mono's allowed. Jon Bliss who built the bike contacted the ACU to confirm these details before he started on the project.

Where some cunfusion enters the discussion is that while the UK ACU rules may allow for recent manufacture of a bike frame for Twinshock class, here in Australia, for Twinshock class there is a major items manufacturing date cutoff of 1987. I realise the motor and wheels on that Bliss bike are pre-87 but the frame is obviously not pre-87.


Here in the UK you can buy brand new £2k twin-shock and "P65" frames, so I guess the ACU had to OK the use of recently made frames on older bikes? None of these is as good as the Jon Bliss TY frame though, and personally I feel that anything with major parts from a later period should run in a "specials" class.

Costs in the UK are already completely out of hand in the "P65" class, with people spending up to £10K on building Brit "Specials" which are allowed by organisers to run as "P65's". The same thing to starting to happen with twin-shock, with the appearance of £7k TY Yams, and cobbled up bitsa RS Honda's built with TLR parts.

In terms of competitiveness though a well built stock 240 or 200 Fantic is far better than the top dollar TY's or RS Honda's, so hopefully TS wont go down the pan in the same way as "P65" has here.

I am confused as to what your stance is - first off you make the point that tricked up bikes like Chris Koch's are needed to compete at the upper levels of TS in the UK. Now you are saying that bikes with major parts from a later period should run in a specials class?
Maybe the odd bike does change hands for 7-10k,but these are the exception,and at club level there are still lenty of people like me riding round on old sheds enjoying every moment.Even if I wanted to upgrade my Ariel it need not cost that much; http://www.ebay.co.uk/itm/Ariel-HT-Tria ... 1c1f667b43
I think there will always be people willing to part with big cash,whatever sport they take part in.I would spend a bit more if my kids were not still at school etc, but I still admire people like Steve Allen who has won the Sammy series for the last few years on a '51 Matchless rigid - its only mods are modern tyres and footrests.
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