Running rich

General Discussion Forum for TRX Enthusiasts...

Moderators: trixynut, Mincehead, dicky, phuk72, Jak, Kevtrx849

Post Reply
TRXNZ
TRX-Enthusiast
Posts: 6
Joined: Tue Feb 05, 2019 12:24 am

Running rich

Post by TRXNZ » Wed Jan 08, 2020 5:08 am

Hi all, I'm after some carb advice. Now my bikes back on the road, the rich running issues are also back ( it had a very clogged filter and I hoped that was part of it) so I'd like to start simple and check mixture screws and needle positions b4 I get too carried away. I've had a look at the manual but it's fairly vague.

Firstly, is there a external mixture screw? The manual talks of one and states 2 turns from closed but I can't see what the diagram is a view of.

Secondly, I'm assuming the needle has various grooves to alter height, do I need to remove the carbs to get the slides out and what clip position is standard?

Any advice appreciated, my bike is a Japanese model with a pumper carb if it makes a difference.

Paul

User avatar
dicky
Site Sponsor / Administrator
Posts: 1051
Joined: Thu Jan 06, 2005 11:26 am
Location: Ruffy, Victoria.

Re: Running rich

Post by dicky » Wed Jan 08, 2020 6:31 am

I assume that you have the factory service manual, it's in the download section if you don't already have it.
Chapter 6 shows the carbs in detail, page 6.2 shows the exploded view of the carbs
This shows the carbs in the orientation as they are installed, left is to the front of the bike.
Part #16 is the pilot screw assembly.
Look at the float chamber (part #2), see the semicircular indent at the bottom? That's where you get access to pilot screw.
When assembled it is almost directly underneath the float chamber drain outlet.
The last diagram on page 6.4 is looking up at the bottom of the float chamber.
To get to the needle you need to remove the diaphragm cap.
You may need to take the carbs off the inlet rubbers to be able to get at the screws.
I find that it pays to replace the Philips head screws with Allen head screw, just be careful when you tighten them as it's really easy to strip the thread out of the carb body.
Take care not to lose the little o-ring shown on the third diagram on page 6.4
With the cap off take out the spring, remove the diaphragm and slide, shake out the needle.
Standard position for the clip is 3 from the top, ie in the middle.
If you are running rich then maybe drop the needle further down into the jet by moving the clip to 2 from the top.
When you put it back together take care that the diaphragms are properly seated in the carb body, otherwise the cap will crush and maybe tear them. This would be bad.
If you've got the carbs off you might as well change out the main jets as the standard main is #142.5 but this is way too rich, you are probably better off with #137.5
dicky
OOOSDC #5

TRXNZ
TRX-Enthusiast
Posts: 6
Joined: Tue Feb 05, 2019 12:24 am

Re: Running rich

Post by TRXNZ » Wed Jan 08, 2020 10:36 am

Thanks Dicky, yip I was looking at the manual on the forum, makes it hard to figure out when you can't see the screw..
A few guys on the Facebook page helped me find it and I just checked them, left pot was 1.5 and right was 3.5 from fully closed. Do you know which way is richer/leaner? I'll pull the slides out tomorrow and check the needle clip positions.

User avatar
dicky
Site Sponsor / Administrator
Posts: 1051
Joined: Thu Jan 06, 2005 11:26 am
Location: Ruffy, Victoria.

Re: Running rich

Post by dicky » Wed Jan 08, 2020 11:18 am

Leaner is clockwise.
You should set the pilot so that the bike runs at a steady idle and does not drop or hang up when the throttle is blipped.
Factory Pro make a really shit, as in crappy and do not use it, carb kit for the TRX, but the CV tuning guide is all good.
http://www.factorypro.com/tech/carbtun.html
dicky
OOOSDC #5

User avatar
dicky
Site Sponsor / Administrator
Posts: 1051
Joined: Thu Jan 06, 2005 11:26 am
Location: Ruffy, Victoria.

Re: Running rich

Post by dicky » Wed Jan 08, 2020 11:40 pm

A couple of other points that may help...

1. Read this...http://www.trx850.com/phpBB_forum/viewtopic.php?t=10899

The original jet needle, aka The Needle, and needle jet , aka The Emulsion Tube, wear over time.
This will cause the bike to surge at part throttle openings, most noticeable when you are cruising on along at constant speed.
More precisely, the emulsion tube gets worn by contact with the needle, causing the inside of the tube to become oval in shape instead of round.
You need to pretty much pull the carbs apart to get the tube out, but once you have it will be clear to see if it is worn.
There are replacement kits for these parts, Factory Pro seems to be popular but be warned, do not use their needle unless you intend spending a lot of time getting your bike to run properly afterwards.
Factory Pro are in the USA, they never had a TRX to develop the kit. It was developed for a 360 degree TDM motor.
Their needle has a very aggressive taper at the tip compared to the stock TRX needle.
See the comparison here... http://www.trx850.com/phpBB_forum/viewt ... 37&t=11183
Their tube is fine to use and it seems to eliminate the wear issue.

2. If you go down the path of replacing the main jet, don't be surprised if the o-ring disintegrates when you pull the jet out.
You can get a complete carby seal kit from Litetek in Thailand, they are worth it.
http://www.litetek.co/Carb_Kit_Yamaha_TRX850.html
dicky
OOOSDC #5

Post Reply