Sidecar MX pics - Post them up here

[270YAM]

whats the 270 degree bit. is the crank different to a standard XS?

Hi Hoony, yes the crank is slightyly different to standard 360 degree XS

That looks great Matt, is that going in the 84??

Spot on Popeye, the EML only ever had the 850 borrowed from the Wasp, now I will have 2 bikes going

[popeye]

Very nice...   I will ring you over the weekend about the Island trip....

[Hoony]

whats the 270 degree bit. is the crank different to a standard XS?

Hi Hoony, yes the crank is slightyly different to standard 360 degree XS

can you explain a bit further 270, you have me interested. is the standard XS rod main pins 180 degree apart or are they inline firing differently? and how does the 270 work?

[shelpi]

Great job 270Yam

[EML]

can you explain a bit further 270, you have me interested. is the standard XS rod main pins 180 degree apart or are they inline firing differently? and how does the 270 work?
[/quote]
Hoony, the std XS fires as a Triumph but if you press the crank cheeks off and spin it, you can get it to 270 (277 actually) and make it fire like a twin/single (twingle ) That way they get drive on every stroke like a thumper. That's the cheep way to do it and it's not exactly right. You can however make it exact if you have the means, which Matt obviously has, and they run even smoother.
It's a bastard of a thing to race against 'cause it sounds like a dodgy old 500 thumper but it hauls soooo hard out of slow turns.
There is an XS forum that will fill you in some more, go there for a look.

[270YAM]

Yes as EML explains, the stock Yamaha is like triumph BSA Norton and any of the early parallel twins with both crankpins in line, both pistons rise and fall at the same time, but on opposite cycles. This results in an even 'firing order' with one cylinder firing every 360°.
The 270° rephase simply means that (in most cases) the right hand side of the crank has been advanced by 90° in front of the left. So instead of the original 360°/360°, it is now 270°/450°. The uneven firing gives the back tyre more time to recover resulting in better traction even though it sounds like 'smooth' power.
 Road racers have been using this theory for a while, Yamaha's latest 'cross plain' crank design in the 4cyl R1 is just 1 example. Power is more manageable and it hangs on better in the wet.

 The crank has a much better primary balance which kills the infamous XS650 vibration, so energy that used to be spent making vibration is now being sent to the back wheel. Free power!
 Instead of accelerating 2 pistons/rods at full velocity and then having to stop then and turn them back the other way at the same time, there is always one piston near full velocity when the other is changing direction- top and bottom.

So we now have a parallel twin that sounds and behaves like a 90° V twin.

it sounds like a dodgy old 500 thumper

Where did you get that from EML?? it must only sound like that when you're behind it!

[270YAM]

Also as EML says, the 277° is an easier and more common mod than the 270°.
The Yamaha crank is basically 2x complete 2stroke cranks joined together in the middle with a 13 spline. If you turn it by 3 splines you can achieve 83.07°/276.92° Crank offset. Close enough to the 90°/270°

[Hoony]

Many thanks guys for explaining this. i never knew this.

i used to swing on a few outfits in early 80's (2 yamaha XS based 880's and a Norton 850)

[Tim754]

Hoony here is some info on a production Yamaha 850 that came with a 270 phase. One of the few bikes I would love as a road bike. They sound so good!

Version History

The TDM 850 was arguably the first road-oriented "Adventure Tour" motorcycle. It was never marketed as an off-road bike, but as a comfortable yet manoeuvrable all-rounder, rather like the later Honda NC700X, CB500X, Kawasaki Versys, KTM SMT, and Ducati Multistrada. When designing the TDM, Yamaha are said to have used a lot of ideas from their "Morpho" project.[1] The TDM's engine was derived from the Paris Dakar winning Yamaha XTZ 750 Super Tenere. Yamaha intended to create a motorcycle capable of handling the mountain roads of the European Alps and coping with rougher road surfaces; and the TDM's "sit-up-&-beg" rider's position was radical in its day.

The TDM was imported into the United States for only two years, 1992 and 1993. It was never a big seller in the United Kingdom or in The Netherlands, but in other European countries (including France, Germany and Greece) sales were strong[citation needed]. In 1996 Yamaha released the Mk2 TDM with updated bodywork and a 270° firing order instead of the previous 360°. This modified engine was first seen on the Japanese market in 1995, when Yamaha introduced the TRX850. The 270° engine gave the TDM an attractive new "feel", and it now became a popular bike in the Netherlands, where for some years it was among the top 15 best-selling bikes.

In 2001 the 3rd incarnation arrived, the TDM 900, with new bodywork, a diamond-shaped alloy frame, a 6-speed gearbox, fuel-injection, R1 derived brakes, a reduced dry weight of 190 kg, a larger-capacity 900cc engine, and slightly wider tyres (160 rear, 120 front). It has a 2-position trip meter, a digital clock, and digital fuel meter. ABS was available as an option.

The TDM is classified as New Sports, a new category invented by Yamaha, comparable with "Dual Sports" or "Adventure Sports bikes". Although a TDM is too bulky and heavy for serious off-road work, its long-travel suspension is well suited for gravel tracks and light off-road use. Popular modifications include fitting aftermarket exhausts, "blue-spot" brake calipers, and dual-sports tires.

As s side  note somewhere amongst my well ordered parts I have a re-phased  crank and camshaft set for a CB754 used with other electrical mods to create a four cylinder twin..  Meaning 1and 4 fire together then 2 and 3.  No I have never put it together but will one day I should.

[270YAM]

As s side  note somewhere amongst my well ordered parts I have a re-phased  crank and camshaft set for a CB754 used with other electrical mods to create a four cylinder twin..  Meaning 1and 4 fire together then 2 and 3.  No I have never put it together but will one day I should.

Hi Tim, the honda 4 motor sounds interesting,

The 4's are simple, just cut the cam in the middle and rotate half of it by 180° and install.
Don't even need to change the ignition as they already fire a waste spark with dual tower coils.
I had a Suzuki GS 750 like that in my '84 EML before I removed it and put it back to how it should be with a big twin.

Many manufacturers make 270° twins now, even the new triumphs and norton's have strayed from their heritage

[270YAM]

270 when you mastered the batteryles ignition setup , I would be interested in a 998 cc 270 project . I reckon in period 4 road racing that setup  would be a contender. Is the 270 configuration also easier to start then a conventional  ?

Yes it should make a great road race motor, still no easier to start though!
Working on battery-less at the moment

[popeye]

Hi guys, I have an almost finished project if some can post the pics would be good??

[270YAM]

Hi guys, I have an almost finished project if some can post the pics would be good??

send em through ill post them for you
matt_270@live.com

[270YAM]

Here is some pics for Lama:

[shelpi]

  Sweet, good work Popeye and Lama ya doing it a treat 

Im trying to work on mine but work and firefighting is takeing its toll :'(