[diyer]

I bought this 2003 Rincon TRX650FA with 2600 miles on it in December 2017 to plow snow and to a little riding.
The carb has never been right.
With the warmer weather I have been trying to fix it.
I have rebuilt it.

It was 35 degrees here this morning.
Good time to test for a cold start.
I'm at 9200 feet in elevation in Colorado.

I start with the start en richer (SE) all the way out.
If I leave the SE out all the way to keep it running it will start to puff black smoke out the exhaust, to rich.
It runs so rich it loads up and will die unless I give it a little throttle to keep it running no matter where the SE is set.

To cure this would I go to a smaller slow jet?
Stock slow jet, S50.
Main jet, 134.
K&N Air filter.
Big Gun exhaust.
After warm up it idles good and runs good.

Again, I'm at 9200 feet so it has to be running rich on the idle circuit.

Any help would be appreciated.

Time for a new carb?

 

[SlammedRanger]

Did the quad come originally from a high altitude area? The carbs will be jetted specifically for the high altitude. If you look in your fsm it will tell you the standard and high altitude factory jetting sizes.

 

[Goober]

Definitely need to swap in a hi alt main jet and adjust the pilot jet in a half turn if you can. Since you’ve also got the KN and modded exhaust the adjustments might not be as straightforward as the manual lays out, but you’ll be close.
Check the service manuals link in my sig block.
When were valves valves last set?
I wouldn’t think you need a new carb but your carb might not be clean enough. Use Berryman chemtool, swabs, pipecleaners, to get every passage. No harsh abrasives. And consider replacing the enrichment valve/oring

 

[diyer]

Thanks guy's.

I have a service manual.
It has a 134 main jet.
I did the valves.
Went through the carb.

It runs good once warmed up.
Idles good.

My issue is cold starts.
It's to rich and has to be baby sat to keep it running.
I can't start it and just let it sit and warm up.

That' why I was asking if I could change something in the carb. to get rid of the rich idling, cold start issue.

 

[misterclean59]

Does this have the plunger style enricher or the old style choke valve? If it has the plunger style then the only thing I can think of is the jet for the enricher is to big. I dont think it is replaceable. It is probably just a hole drilled in the bottom of the bowl. You could try to measure the diameter then fill the hole with JB weld and then drill a smaller hole. Otherwise your bowl may need to be replaced.

 

[SamUK]

I’m assuming that temperature you gave in the OP is in Fahrenheit? If so I would only consider that to be chilly, not cold.
I’ve never had to use the choke (enriched) on my 300fw neither did we on my Managers 420 Rancher.
Have you checked your spark plug colour to confirm your mixture is correct and there are no jetting issues? At that temperature I see no reason why your ATV shouldn’t start without the choke (enricher).

 

[mrbb]

sell it and buy a EFI machine LOL
high elevation plays hell on things with carbs, I would honestly try contacting a local Honda dealer in your area that KNOWS the high elevation settings better, they SHOULD be willing to give you simple info, you can use to set it up correctly for your elevation, once set up correctly, it should run better for you as I have run my carb's sleds in elevation problem free from cold starts to HOT runnings
and my atv's here in basically flat land s(2000 ft) compared to you, in temps from minus 40 to 100's in summer and never a issue's cold running starting or hot
(super cold I do prime carb just to make life easier on it)
but I would ask your local honda dealer ship to get more local info for your atv there

 

[ATC4ever]

How long do you leave the choke on? Might sound obvious, but have you played around letting it idle w/o the choke on or at least turned off a little?

 

[diyer]

Thanks all for your input.

It has the plunger style en richer misterclean59.

Yes, I checked the plug SAMUK. The electrode was tan but the rest of the plug was black. And it is Fahrenheit.

ATC4ever
How long do you leave the choke on? Might sound obvious, but have you played around letting it idle w/o the choke on or at least turned off a little?
Yes.
And it will die unless I give it a little throttle to keep it running until it gets warm enough.

I have been starting it up first thing in the morning.
Yes, it not winter temps but it is all I can do.
Last winter it always started but didn't pop right off all the time.

After the carb rebuild it starts better and idles better once warmed up.
I still believe the problem is it's just to rich when cold.

Yesterday I made a piece that's shaped like a U that slips over the handle bar grip and holds the throttle in a little to give it a little gas.

This worked well.
Slide this over the grip to keep it just off of idle and it doesn't die.
No standing there and keeping it running.
Once it gets warm enough remove my device and it's all good.

Thanks again to all of you for taking the time to respond with your ideas.

 

[SamUK]

If the electrode is tan and the outer and insulator are black (soot) your definitely running rich on one of the jets. Can you confirm the clip on the pilot needle is in the correct position? Usually in the centre, but yours may be different for higher altitude.
I ask the above as you say it was fine last year and that you rebuilt the carb, could be a simple rebuild error.

 

[diyer]

If the electrode is tan and the outer and insulator are black (soot) your definitely running rich on one of the jets. Can you confirm the clip on the pilot needle is in the correct position? Usually in the centre, but yours may be different for higher altitude.
I ask the above as you say it was fine last year and that you rebuilt the carb, could be a simple rebuild error.

I just got this ATV in December.
I wasn't fine when I got it.
I will run it for a while and recheck the plug.

 

[mrbb]

If the electrode is tan and the outer and insulator are black (soot) your definitely running rich on one of the jets. Can you confirm the clip on the pilot needle is in the correct position? Usually in the centre, but yours may be different for higher altitude.
I ask the above as you say it was fine last year and that you rebuilt the carb, could be a simple rebuild error.

I just got this ATV in December.
I wasn't fine when I got it.
I will run it for a while and recheck the plug.

is it the same fuel in it since DEC?
if so, I would be dumping it and starting with NEW fuel
6 months almost and WHO know how long it was in the fuel stations tank, ethanol fuel goes BAD fast untreated and even at times treated, we don;t have GOOD fuel like we did yrs back that would last a LONG time
this ethanol fuel is CRAP if you ask me, meant to be used FAST and that's it

 

[retro]

Your carb has a starter jet in it... see the FSM for its location. You can replace it with a smaller starter jet, OR adjust the tension on the choke knob so it can be partially choked and stay there until you release it. An OEM Honda starter jet for a 350 Rancher will fit it. Check the numbers just in case I'm wrong... But I'm pretty sure the Rancher has a smaller jet.

 

[diyer]

Your carb has a starter jet in it... see the FSM for its location. You can replace it with a smaller starter jet, OR adjust the tension on the choke knob so it can be partially choked and stay there until you release it. An OEM Honda starter jet for a 350 Rancher will fit it. Check the numbers just in case I'm wrong... But I'm pretty sure the Rancher has a smaller jet.

I found the stater jet in the Honda Service Manual.
I thought the same thing, replace it with a smaller one.

 

[diyer]

mrbb.

Not the same fuel.
On the third tank now.
91 octane.
Every tank get's fuel stabilizer.

 

[wheeler]

Can you confirm the clip on the pilot needle is in the correct position?

This will have NO effect on idle/start up.


U say u have black smoke, but also say u need to give it gas to keep it running.... Yes black smoke would be unburnt fuel, however IF u need to throttle it too keep it running to warm up is not enough fuel. So this tells me u should make sure the carb is pristine, plug is good, AF set correctly, choke cable not sticking.... follow me??

 

[mrbb]

also, just for kicks, I would do a compression test here on this atv
lower compression can lead to idling issue's too! and cold starts!

 

[diyer]

Again, Thanks Guy's.

Plug is new.
AF screw is set correct. Spent a lot of time setting this screw to get it right.

I think I may be leaving the Start En richer on too long.
After I get it adjusted, it stops puffing black smoke.

Beginning to believe this may be operator error due to a lack of experience with this ATV.