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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Crankcase breather
Post Info TOPIC: Crankcase breather
Gazztop


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Crankcase breather
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Hi guys quick question for ya,I’ve just bought this bike and noticed it has a bad oil leak from the top end somewhere,I rode it briefly the other day and it was way too bad,it seemed to be leaking out at pressure,as if there is no crankcase breathers,so I go and investigate,and I can’t find one on there at all,all I see is this blank type plug where it should be,any ideas please people? Many thanks ,Gareth



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TTRfan


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Hi Gareth

The blue TTRs invariably have the breather on the camshaft cover.

It is very rare for a TTR to leak oil (in the way that classic Brit bikes do)  other than from the decompressor blanking plug just above the exhaust port.

See here

Brian



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Gazztop


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Hi Brian,thank you for your info it’s a great help,I just needed to make sure the previous owner(sss) hadn’t cowboyed anything just to cut corners etc,I thought this as there’s a blank in the inlet pipe from the air box to the carb (pictured) I’ve looked for info on this part but not been too successful yet, I’m guessing it’s some type of recirculating system,



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TTRfan


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You have guessed correctly - your airbox is missing the emulsifier - the "clean air" gubbins - see photo below:

Emulsifier 1.jpg



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TTRfan


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If you are unsure of any parts it is always worth looking at the fiche on Fowlers or other Yamaha parts dealers which have the exploded diagrams of all the parts.

This is the one for the airbox:

airbox_fiche.jpg

 

It would also be useful for you to grab a copy of the workshop manual. There are several freebies on the interwebs to download but see those available at Totally TTRs here. They are cheap enough and it supports the only specifically TTR250 parts shop that I know of wink

Brian



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mossproof


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The part that is missing/blanked off by a cowboy, is the resonator box, see here:

ttr250.activeboard.com/t51169250/yamaha-energy-induction-system-yeis-boost-bottle-air-chamber/

As Brian says, the most likely culprit for oil leaks is the decompressor blanking plug.

The cyclone/emulsifier is still there as far as I can see on your pic, and the long tube approx 14mm diameter that is attached to it goes to the breather at the top of the cam cover, which is where the crankcases breathe from on "Blue" bikes.



-- Edited by mossproof on Tuesday 5th of July 2022 10:59:25 AM



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Gazztop


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Good morning and Thank you very much chaps,your info is most helpful,I’ll grab a copy of the workshop manual also,
With regards to this resonator box I’m missing,how important is it and should I try and source one or is it no big deal?
Thanks,Gareth

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TTRfan


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Simon's eyesight is better than mine and he is, of course, absolutely right in that you are missing the resonator box disbelief

If you follow his link to the thread about the box then you will see that the informed opinion is that it is a Good Thing so worth getting ahold of one wink

If you contact Steve at Totally TTRs then I am sure he would be able to sort you out a good second-hand box biggrin

Brian



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KiwiJeff


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When I bought my TTR that Box was missing and I thought it was not really needed.
Thinking that Mr. Yamaha had put it there for a reason so I bought one and put it back on and it seemed to give the bike better low down power.
I could be dreaming but .....
I was told that it probably had something to do with “Air Pulsing” on the Intake.
Cheers
Jeff


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TTRfan


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Steve now has a resonator box in the shop - see here



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KiwiJeff


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Thanks for that follow up Brian.
It’s good to know that I did the right thing by putting one back on.
Also, my feeling that the low down power was increased, looks correct.
Before I put it on, I did a Test Ride up a favourite local hill, where I have to change down at about the 3/4 mark but with it fitted the change down was further up the hill, or not needed at all.
Not a completely Scientific Test but works for me !
😬
All the best to you Steve and your families.
Might come back again one day to check out those Pasties 🥟 and Beer 🍺
Jeff



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TTRfan


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KiwiJeff wrote:

All the best to you Steve and your families.
Might come back again one day to check out those Pasties 🥟 and Beer 🍺
Jeff

All well here thanks biggrin

Be good to see you again Jeff!

Brian



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ttr steve


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You would always be welcome here smilesmile



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KiwiJeff


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Very kind Lads.

Just watched the TV News and you folks are getting some excellent temps at the moment.

Good time to be throwing those TTRs down some Devon Green Lanes. 🤪

Cheers

Jeff

 



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