McVick's NX650!

[Brian McVickers]

I am trying to re-jet the carburetor, I've followed the Honda Service Manual instructions to the point that the seat, fairings, fuel tank and separator are off.

Next on the instruction list is to remove the Carburetor Insulator Mounting Bolts. There are three of them, all hex hed 5mm. After these bolts are removed you are supposed to detatch the throttle cable holder from the carb , loosen the clamp to the airbox and then move the Carburator and Insluator assembly out through the left side of the frame where the Separator was.

These three bolts will not move. I have PB Blasted them and even used a small cheeter bar on a 5mm allen wrench. I got one of them to click once, like it was about to turn freely but it won't move. When I got to the point that the allen wrench started to strip the inside of one of the bolts I stopped. (And yes, I was turning the bolts to the left to loosen - counter clockwise

Any ideas or help would be greatly appreciated.

Thanks
Brian

 

[goodtimes]

Heat may help.

I have not looked at the on a NX650...but my rat-bike ('80 CM400) has just enough room to remove the carbs without removing the "insulators". It is much easier to take it all out together though. I doubt you will be able to jet the carb without pulling it. Well, there is *always* a way....but probably not a realistic way.

Sorry, I'm not much help without putting my eyes on the bike...

 

[mhiscox]

Heat may help.

I have not looked at the on a NX650...but my rat-bike ('80 CM400) has just enough room to remove the carbs without removing the "insulators". It is much easier to take it all out together though. I doubt you will be able to jet the carb without pulling it. Well, there is *always* a way....but probably not a realistic way.

Sorry, I'm not much help without putting my eyes on the bike...

What he said. I don't know much else to do besides heat, penetrant and maybe a few gentle vibration-inducing raps with a hammer.

I've also gotten carbs out to the side by leaving the isolator behind, but it depends on the individual bike. I don't imagine there's much harm in trying. I also agree that you probably can't rejet the carb in place (the jets/jet holder are soft and really easy to crossthread/strip).

If you fall into the area where you can't get the carb out of the frame to the workbench, but do have enough slack in the cables and room in the frame to turn the carb 90 degrees toward you, that might work. You probably can successfully swap the jets if you can see what you're doing; you may not need to totally remove the carb. But I wouldn't try it blind.

But I, too, am guessing. I've ever seen an NX650 in the flesh, so to speak.

 

[Brian McVickers]

Thanks for the input guys,
Here are some pics

The bolts in question!

The carb assembly and the hole where it is supposed to be removed through.

A close up of the Insluator, its flange is triangular with two bolts on top and one on the bottom.

 

[goodtimes]

Brian,

You can always get a small pair of vice-grips on the outside of the bolt heads that are accessible. You will want to replace those bolts afterwards...but honestly, I would replace them all anyway since you are bordering on stripping the heads out already.

You may be able to get the carbs out through the back...but it looks like you will have to remove the air box first...which may require you pulling the rear inner fender, which may require pulling the outer fender, which may require pulling all the lights, tire, etc....

I'm not sure what type of carbs you have. My CM400 (Honda) has CV carbs plus enough room to pull the metering rods out from the top, without removing them from the engine. I have recently moved the metering rod stop up, which increases the fuel flow, relative to the air flow (making it run richer -- which is what you are trying to do). Adjusting the metering rods should have a bigger impact on the mid-throttle range, while changing the jets has a bigger impact overall, including idle and WOT -- where the metering rod adjustment will have a smaller impact (at least this is what a number of carb-tuning references I have found on the web have led me to believe -- I am far from an expert on the issue). My problem was with mid-range performance, so I went that route (plus, it is free, and easier than changing jets). If you are just looking to kill a lean spot in the mid-throttle area, this may be easier since you are having trouble with removing the carbs.

Again, I'm no expert, and I don't know how easy it would be to accomplish that on your bike...if it is even possible.

 

[Brian McVickers]

Thanks,
My plan as of now is to remove the rear fender, remove the airbox andpull the carb out the back. Who knows, maybe I'll have a better angle on those stuck bolts with the carb removed.

Brian

 

[Hltoppr]

I don't recall that you need to remove the entire carb to change jets....

I've got a call into the PO regarding jets....

-H-

 

[Brian McVickers]

Thanks Andrew!

 

[Brian McVickers]

Ha Ha! Victory.

I present to you a Keihin CVK40 Carburetor, commonly found on the NX650, the XR650L and the KLR650.

I removed the rear fender and battery so that I was able to move the Airbox back enought to disconnect the Carb from the Airbox in the back and the Insulator in the front, then pulled it out through the top fof the frame.

Then after the Carb was removed I figured I would give the bolts on the Isolator another try. Using a 5mm allen socket on a ratchet I was able to free and remove two of the bolts but now the first one I tried will not come out becuase it is stripped and I can't get any purchase on it. Not sure how hard I will pursue that but I woud like to get it out and replace it.

Thanks for all the help and ideas.

Now to take the Carb apart! :wings:

Brian

 

[goodtimes]

Brian,

They make special sockets for stripped out socket head cap screws (what you have). They look pretty much like every other hex bit, except the edges are sharper, and the whole thing is tapered. The end is the "right" size, and it gets bigger as you move towards the ratchet end. You simply pound it into the head of the cap screw like the square easi-outs, and hope like heck it holds tight enough to get the bolt out.

IIRC, I have bought them through Grainger before....but any industrial tool supply should have them, or be able to get them fairly quickly. You probably won't find them at Home Depot or Sears...but you could certainly try.

That carb is similar in function to what I have on my Honda (also a Keihin -- well, actually I have a pair of them...)

 

[Brian McVickers]

Thanks Brian,

So I am a bit baffled.
The carburetor has the stock jets in it, Main 155 and Slow 48. This means that the carb jets were never changed out previously.

I called a local Honda shop to ask thier opinion as I was wondering about maybe having them look at it and they told me that this bike just acts how I described and theres nothing wrong with it. I think I need to have someone else who has more expereince on different types of bikes try mine and tell me what they think.

My learning curve on bikes is pretty steap right now and I think the lesson for the day is that not all bikes are the same. This bikes behavior at low rpm is different than other bikes I have ridden so I assumed there was an issue. Maybe there is, but it's nothing bad just minor tuning for altitudes.

I'm going to clean the carb while I have it out and then put everything back together and go ride!:bike_rider:

 

[goodtimes]

You are right, bikes are all different.

Thumpers act differently than parallel twins, which act different than horizontally opposed twins, which act differently than in line fours, which act different than, . . .

Even beyond that, not all thumpers act the same (or all parallel twins, etc).

You could ask around over at thumpertalk.com, or ADV rider and see if there is anyone in the area who has a Nx650...you could get together and compare notes.

ADV guys (and gals) are notoriously friendly, once you get past the "ADV Salute".

But, I think you have a good plan. Clean the carb up, and go change the fuel in the tank a few times...

:bike_rider:

 

[GSer]

A friend of mine bought a low mileage 1999 Suzuki DR650 last year. The engine would just randomly shut off while he was riding it. After cleaning the carb., including the jets, the problem didn't go away. He ended up buying a complete carb. rebuild kit from the Suzuki dealer. Installing the kit fixed the problem, although he isn't sure which particular part was causing the problem. Have you been able to find a rebuild kit for your carb.?

 

[Brian McVickers]

The issue is no where near as bad as the engine dying. It is just not as smooth as it was at altitude, a mixture issue.

 

[Brian McVickers]

Ok, new game plan,
I got the chance to talk with an old-school Honda moto mechanic.
He said that since the jets are the stock #155 and #48 all I should need to do is raise the needle. He said to move the c-clip on the needle one groove up. I soon discovered that the needle in this carb does not have a c-clip or grooves so the answer from the local shop is a few very small washers to place under the head fo the needle.

At the same time I have decided to install a larger Pilot Jet, supposedly these engines came from the factory very lean, which can cause the engine to run hot, so I will be making the change from a #48 to a #50 and fine tuning it with the idle mixture screw.

I'm convinced on the adjustment to the needle and somewhat on the pilot jet but I figured making the change now may save taking everything apart again.