86 replies to this topic

[Studley Ramrod]

£10.80 each inc. vat at NRP fer, and oi quote "exactly equivalent to 5G52, made like the original in aluminium alloy"

Mk1 - http://www.nrp-carbs...product_id=4131
Mk2 - http://www.nrp-carbs...product_id=4134

[Hombre]

Studely,

Thanks for that - much more sensible price. I see they also do emulsion tubes at £16.80 ea.

[Studley Ramrod]

Yes they do, but the FP emulsion tubes will last a lot longer than them.

[nigel2129]

Huge thanks Paul for the original feature which gave me the confidence to tackle the work so over the last few weekends when I have had time I've replace the emulsion tubes and alloy needle jets both from NRP. I've also replaced the inlet rubbers as they were perished and breaking up,
Lastly the the choke cable was stretched so replaced this too as well as cleaning the choke linkage at the carb end as pretty filthy.
I only decided to tackle all of this because I was being informed by fellow riders that it smelt extremely rich sat behind me at lights etc and the choke as it was was pretty useless but apart from that it was running fine so fingers crossed it starts tomorrow as I have a day off to put the battery and fuel tank back on so fingers crossed,
I also took the opportunity to replace the O ring and jubilee clips on the thermostat as had a very small leak,
I'm glad I SORN'd my tdm for the winter to do all of this at leasure so providing it starts fine tomorrow it's straight I for an MOT and away we go
I've been riding my my Honda deauville throughout the winter but can't wait to get the tdm out because as to state the obvious these bikes are completely different to ride and I absolutely love riding the tdm

[dandywarhol]

I've been having a problem with fuel leaking past seals on my TRX being affected by ethanol in modern fuels. 

 

I've just received a set of Viton seals from a Brit based out in Thailand. Nice kit, nice price, quick delivery and a "How to do" section on the website Litetek

 

http://www.litetek.co/ 

[dapleb]

Noice wan wee wan.

[cookiebare]

Huge Big Thanks m3psm for posting this. I bought new emulsion tubes from factory pro a couple of years ago and have not put them in for want of a bit of clear guidance and lots of Pictures. Hope to get into it this weekend.

[Got1now]

Well written (and photographed) post. I'm at the point of pulling the carbs off my newly acquired 850, as the previous owner had problems with it running rich, so I will first check the choke mechanisms, in case they are sticking, but then it'll be a look at the emulsion tubes.

As it's a 1999 model, and I read that the emulsion tubes can't be changed on the later Mk2 850's, what is the solution?

Has anyone successfully replaced the emulsion tubes on a late MK2, or is there another fix?

I've a fair amount of experience with Brit and Italian carb strip and rebuilds, so I'm not phased by the work, but would appreciate any info that you guys can supply.

Cheers......

[Studley Ramrod]

If they are '99 carbs, the toobs are pressed into the carb body.  I know not how to remove them or press the new ones in.  Kedo.de used to sell the toobs, tiny little things they are.

Pretty sure someone has done them, can't remember who though as it was a few years ago.

[Got1now]

If they are '99 carbs, the toobs are pressed into the carb body.  I know not how to remove them or press the new ones in.  Kedo.de used to sell the toobs, tiny little things they are.

Pretty sure someone has done them, can't remember who though as it was a few years ago.

I should know tomorrow if the carbs are the later models, but the bike was first registered in March 1999, so who knows, maybe I'll be lucky, and have the earlier carbs......if not, I'm just going to hope someone here has a solution.

For every problem, there has to be a solution........

[GrandPaul]

QUOTE(92 3VD @ Tue 22nd Apr 2008, 06:34 PM) <{POST_SNAPBACK}>

Thomas here from the US...

The emulsion tube (brit name) is simply the tube that holds the jet needle in the carb.
What happens is the tubes wear from a round hole to an oval hole as the needle moves in and out.
Being a round needle in an oval hole you tend to get excess fuel leaking in past the sides.

There could be other reasons for the 'popping and spitting' (like air leaks in the carburator system).


If you look closely you can see the 'ovaling'
(The green inserted circles are perfectly round, you can see where both sides 'ovaled off' past the green.)

Replacing worn emulsion tubes will not only restore performance it will increase the fuel economy.

 

Thanx, Randy, for asking my question.

 

Thanx, Thomas for a clear and concise answer.

 

We refer to those bits as "needle jets" in classic Britbike lingo, but I believe the parts books list them properly as emulsion tubes.

 

Of all the Britbikes I've owned, only the Norton Commandos used the square cutaway on them, just like the TDM. It is supposed to cure hesitation on quick throttle opening.

 

Very nice indeed. Thanx, chaps.

[yamageo]

Hi, would worn emulsion tubes cause the bike to rev excessively,cough and splutter. I have a 1992 tdm which now won't start, when removed the plugs they seemed wet.

[Studley Ramrod]

Not really, sounds like you might have a different problem.  Worn toobs tend to show themselves as a smell of fuel and poor economy when running mid revs.

[abennett]

I started on this but found holes in my diaphragms. I the US they are going for 100.00 USD each! Is there a source where I can get them for less money? I am working on a 1992 850.

[Apache]

I started on this but found holes in my diaphragms. I the US they are going for 100.00 USD each! Is there a source where I can get them for less money? I am working on a 1992 850.

56 gb pounds a pair over here chief from nrp diaphragms. I'm sure they'll mail them. Hth..
p.s. might as well do the tubes while you're in there. Same source..

Edited by Apache, 02 January 2018 - 08:16 pm.

[maelstrom]

Hello everyone,

I am Blair and our business is LiteTek. I am not trying to sell anything to you.

Sorry I don't have a TRX just a 4 cylinder. Anyway one of my customers mentioned the forum and I know that the needle/emulsion tube wear for Mikuni BDST's is worse for big twins.

Anyway I thought to give some of my take on this.

First of all the wear occurs at idle where the needle is closest to the emulsion tube and the pulses are ratting the poor things to death. So there are two parts to improving this.

 

Part 1 - The Needle:

Reduce the tendency for the needle to vibrate as much as it does. On the 4 cylinder 250cc Yamaha the same problem was addressed in the very last models by sealing the top of the needle. As shown in the first pic.

 

Honda do something similar with the downdraft carbs on their 250cc four.

 

This sits over the top of the needle and totally seals it.

 

Now trying to do something like this with standard BDST will prove to be difficult. My idea was to machine an o-ring groove into the needle bore in the slide. Fit an o-ring and the needle passes through that. Just haven't got around to doing it and to make matters worse I just got a set of FCR's.

 

Part 2 - The Emulsion Tube

So these being made of brass is not good from a tribological point of view. So what I chose to do was to sleeve some used emulsion tubes with a polymer. 

These are machine reamed and checked with pin gauges. Now the customer that I did these for has not used them, so much for our field trials. If one of you guys would like to try a set out then give me the number of your worn emulsion tubes and I will see what bits I need to get. If it is doable then I could do them for you and you could try them out.

 

Some of you may have seen my guide for BDST's here. https://litetek.co/G...ST_Rebuild.html  and this is the Keihin version I did which has some extra hints that I have not put into the Mikuni one yet. https://litetek.co/G...in_Rebuild.html

Cheers

Blair

 

 

 

[dapleb]

Hello dare Blair and welcome,

That looks loike a neat solution. A number of us have switched to the factory pro mulshions which are much less marsh mallow than OEM.

Your idea looks like a neat idea and if/when me factory pro juans give up I would def give those a try.

[Studley Ramrod]

Yamaha also addressed the rattling issue on the TDM850 by replacing the BDST38's with the BDSR38 carbs for the mk2a TDM850.

 

http://www.carpe-tdm...20351&hl=bdsr38

 

I'm planning on stripping my mk1 carbs down over winter sometime, I've got the litetek service parts to fit, so will contact you with the parts numbers if you haven't already got them from another member.

[maelstrom]

Aah there you go. O-rings to seal the needle on those BDSR38's as well.

I just wanted to know the emulsion tube numbers so I can calculate what reamers I would need to buy etc.

[dapleb]

I expect either studder or oi have an old set knocking aboot if you just need a number off em.