Carb to filter rubber
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The idea of Yamaha's "Yamaha Energy Induction System" (YEIS) was developed in the early eighties to comply with the new exhaust emission standards in the US at that time.
In theory, the idea was to conserve some of the air momentum via this box and help fill the crankcase at the next stroke. Yamaha claimed this had an effect on both fuel efficiency and power. But it was later discontinued and I can't remember that any other motorcycle brands did something similar. -
@GeirA when was it discontinued? This was ran on all DTR models right up until their very last model.
And yes YAIS was their other mechanism from the exhaust. I don't know why I put that.
Ultimately Yamaha is a massive company and if they didn't think it did anything then they wouldn't have wasted the money manufacturing the bottles for so long.
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@markus-w said in Carb to filter rubber:
@SpookDog
Yamaha DT125R Boost bottle yeis chamber 2 DTR DT125 DTR125 YPVS TZR GPR SC125The YEIS chamber sits on the inlet manifold above the reed block
The chamber on the side was only fitted to the later models and I'd assume was some kind of intake silencer rather than a performance related part
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@Calum as you know, DTR was first released in 1988 and even though YEIS has been a part of the intake system on the DTR throughout the years doesn't mean it did very much for the performance in either way. And because YEIS wasn't implemented in any newer two-stroke models from Yamaha may confirm that. YEIS might also have been more of a marketing strategy to keep two-strokes popular in a time when four-stroke engines began to take bigger market shares.
Yes, Yamaha could have removed it, but that cost resources and money. So why change something that probably just doesn't matter either way? Yamaha is also a company that are reluctant to change motorcycle models that still sell well, like the DTR. Yamaha YZF ThunderCat was another motorcycle that was sold for many years virtually unchanged. In Asia and South-America there are models designed in the 70s that still are produced and still sell well in those markets. They aren't even manufactured in Japan. Actually, Yamaha has a lot of factories around the world that produce the same models year after year, and models we will never see in Europe or the US. Even the design of some models is done outside Japan. I know for sure that Yamaha DTR 50 was designed and produced by MBK in France, not Japan. -
@GeirA What’s your point? lots of 2strokes in the 1980s used ‘boost bottles’ - YEIS was used on big bore IT’s and YZs from the early 1980’s.
It was deemed an improvement on engines that are now over 30years old in design.
2strokes were still being understood well into the 1990s,
The second YEIS bottle was added to the DTR for the 2000 model year
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Yamaha just refer to both of them as Air Chamber on the parts diagram's - I still say its not a performance item and its just a bolt on for emissions / silencing etc.
Yeah I don't know.
