Fun with TurboT's Gio Beast
 

T left me alone with his quad, and I got bored.

I chopped the hideous (and heavy) stock muffler off of the pipe, flush with the end of the muffler. The muffler corrects the angle of the pipe, so a flush cut was the best move for future consideration (more on that later). I intend to experiment with a Gio muffler that is intended for a 125 Pit Bike. That sounds kinda small, but the pipe diameter actually matches the Beast. I have experience with the Pit Bike muffler, and it's a hot rod piece.

Here's the side view of the chopped pipe. I kind of like it this way, but it would likely start the carb and filter on fire.

http://i158.photobucket.com/albums/t...edpipeside.jpg

It's deceiving from that angle. Here's the pipe from the rear.

http://i158.photobucket.com/albums/t...edpiperear.jpg

Here's the future consideration I spoke of. T might want a Monster muffler installed eventually, and here's a mock-up of one I had laying around.

http://i158.photobucket.com/albums/t...erpipeside.jpg

I entertained the thought of just attaching the muffler to the chopped pipe and calling it a day, but it'll likely hit the tire on suspension compression, and there's nothing to attach it to.

http://i158.photobucket.com/albums/t...eanglerear.jpg

Dig that stinger look.

http://i158.photobucket.com/albums/t...eangleside.jpg

I decided to weld in a piece of pipe to connect the chopped pipe and the Pit bike muffler. I attached the muffler to the rear rack mount via the supplied clamp. That welding blanket is made by Levis.

http://i158.photobucket.com/albums/t...esidefinal.jpg

Here's the rear view. It looks straight. Sorta.

http://i158.photobucket.com/albums/t...erearfinal.jpg

I'll fire it up tomorrow and find out just how obnoxious it is. Stay tuned.

YOU ANIMAL! WHAT'D YOU DO TO MY QUAD??!?! :evil:

Now I'm gonna chop your old muffler into tiny pieces for the entertainment of the forum.

Teach you to leave your quad at my house.

Well you know I'm here for the entertainment and learning of others. :)

Looks good chap. Can't wait to hear that pipe sing, maybe we'll get flames too?? :)

i was thinking of doing the same thing puting a 125cc dirt bike exhuast. got any sound clip of your exhuast??? how does the power feel

Battling a no-start issue as we speak. I thought I found it in the plug wire, but still no joy.

Further bulletins as events warrant. :D

Grab the Brake.........lol

try to play with you kill switch that what happens to mine or check your spark plug if it is not full of gas that happen to me to.

You need to grab the brake to start these?? 8O

That quads been a bit of a beotch to start since I got it.

not only thes atv a lot of new ones too my uncle has a 2008 ds450x and he has to hold the brake and the clutch to start it

Safety 1st...

TurboT's kidding; it's his quad. The brake switch has been confirmed by the brake light and spark (yes, tried other plugs). I think that the new muffler has leaned it right out. Anyone have an idea about how much I should drill out the idle jet? The stocker is a 20.

While on that topic, I'd like similar info on the main jet (currently a 100). I realize that I can buy these, but everything is closed right now. I know that Keihin carbs have a direct metric relationship, but I'm not sure if a Mikuni 100 means 1.00mm.

It this the stock or performance 125 pipe.

play with the carb just rich it a bit it will start

If it won't start with full choke then i doubt the idle jet is your problem, unless it's plugged. I must asked if you have washed it lately?, everytime i wah my son's 50cc it won't start til 24hrs later, there fuel, spark but it just won't start til the next day, time for some dielectric grease for me.

Yozalo, yes, it is the 125 Perormance Pit Bike muffler.

waynev, the quad has been nice and cozy in my shop for some time, without getting wet. It was running on the weekend after the 30mm Mikuni installation, but it hasn't started yet with the new pipe.

you just need to adjust the carb

Success! It runs.

Prior to success, I had removed the carb and blown air through the passages, and tried the air / fuel screw all the way to 3.5 turns out. As previously mentioned, I think there was a spark plug wire issue, so I swapped it for an NGK cap and wire. Still no joy.

I took the carb off (again), and this time I removed the main jet and the idle jet, along with the float valve and seat to make sure that nothing blocked the passages. There was nothing in there; no dirt, no casting flash, nothing.

I read linuxman's post (http://www.chinariders.net/modules.p...ewtopic&t=8904) about his experience with a 30mm Mikuni, and it seemed reasonable that the 100 main jet was the culprit. After some measuring, I discovered that the main jet and the float valve seat are metric references (100 means 1.00mm). I'm not so sure about the idle jet, because it necks down inside, so you can't likely modify it by drilling it out.

1.00mm winds up right between a #60 and a #61 drill bit. Following linuxman's advice, I wanted to get closer to 1.05mm, so I drilled out the main jet to 1.04mm using a #59 drill bit (0.041"). A #58 bit would have opened up the jet to 1.07mm, and I don't want to go that far yet.

Upon adjusting the air / fuel screw to 2.5 turns out and re-installing the carb, it fired right up. It still takes the better part of five minutes to properly warm up, but it runs. Sounds mean with that new exhaust, too. 8)

http://i158.photobucket.com/albums/t..._Beastruns.jpg

Sweet mate. Sounds good.

Good investigative work. I did a little hunting for jet charts, and found nothing useful to me other than suspected you were correct to need to jet it.

Was drilling out the jet a better soloution than moving the clip?

Even if you could have fixed it by moving the clip I would understand fixing the root cause first, that way you still have all your clip adjustment open to you. Am I on the right track or did you HAVE to do the jet?

Yes, i have a #41 bit :) :)

Hey Pete,

W&G can confirm, but I believe the clip was at it's richest setting when we first put it on... so there was no wiggle room there which left the jet.

I never looked at the clip, but I distinctly remember W&G doing so and saying as a reminder to himself and me it was at the richest setting.

Of course, now he'll come around and tell us that wasn't the case, and that I had been sniffing way too much gas fumes to remember my name, let alone the needle setting. 8O

Right, thanks there Turbo, I totally forgot our Mikuni carbs already came on the richest setting. Bigger main or drill it out would be the next options.

Sigh..the older I get the more "seniors moments" I have....

One thing to remember on the mikuni carb is the main jet only controls the mixture from 3/4 to full throttle, that's it, and the only way to check if it's proper is a wide open run and kill the engine at full throttle and then inspect the spark plug.
Also most engines will like 1 main jet size up or down per 7 deg C temperature change, so if it runs good in the summer at 20C on a 100 jet, then when it gets to -1 you should be running a 130.

Waynev, that's almost exactly what I was struggling with. It has been my understanding that the main jet controls the mixture at tip-in, but now I'm inclined to question that.

The main jet is (as we're all aware) directly below the slider needle. As soon as the throttle is opened, the needle is pulled up from the jet, uncovering the orifice. It seems to me that if the orifice is a larger diameter than stock, more fuel would flow upon opening the throttle (I think we can all agree so far). The thing that hadn't occurred to me is that since the idle speed screw simply lifts the slider, the main jet is uncovered even at idle.

To support this, I made no other mods and the quad fired right up. It still has a bit of a 'hunting' idle upon blipping the throttle, but I think that's something else. Maybe I just crutched it, I dunno.

I noticed a mis-match between the intake tube insulator and the new Mikuni, inside and out. A person would need to hog out the ID of the insulator to get maximum benefit from the new carb. The o-ring on the Mikuni isn't completely covered by the outside of the insulator either. The easiest fix would be an insulator that is designed for a 30mm Mikuni or Keihin round slider carb.

I'm not convinced that the stock insulator isn't creating a vaccuum leak. Anybody else have idle trouble?

Maybe a bigger idle jet will solve the idle issue; I'll see about picking one up today. The symptom remains that when you blip the throttle, it takes 2-3 seconds to come back to idle. That's despite re-routing the throttle cable to a more relaxed radius. BTW, it had the same symptom with the smaller carb, but it was worse.

Pete, to be clear, I used a #59 bit, which is 0.041".

Cheers!

Sorry W&G i can't agree with that statement, the larger main jet will not flow more fuel until you are over 3/4 throttle, it is the taper on the needle jet and the jet needle that controls the flow from 1/4 to 3/4's. Think of it this way your needle jet/jet needle is a 1/2" garden hose, even if you hook up a 2" hose to the 1/2" hose it won't flow any faster.


There's a nice explanation and a chart of throttle postions and what is the control for eash position here, http://www.iwt.com.au/mikunicarb.htm

Hey D,

Since we're on the subject of vacuum leaks have a look at where the intake manifold bolts to the head as well. While we were installing the carb I was looking around and noticed there seems to be a bad fit between those two items. I was looking at it and wondering if it was a problem, then got distracted by something else. It might be nothing, but might need a little goop there. :)

When I mentioned the racing idle and slow return to idle with Pop's, the first thing out of his mouth was vacuum leak, while we assumed it was the throttle cable I didn't think too much of it agian.

I noticed in your video the slow return to idle, but had assumed you had not rerouted the cable until I read this.

nice video good job on that exhaust mod

Of course your right waynev. I forgot about the needle taper.

I ordered a new idle jet today that is 22.5 instead of the stock 20. It should be in tomorrow, so we'll see if that helps.

T, I intend to remove the insulator completely, since the Hondas don't use one, and the o-ring on the carb should mate nicely with the intake. I'll check the intake to head relationship as well. Does anybody have a favourite method for checking for vaccuum leaks?

BTW, the quad wouldn't start this morning (I didn't try very hard). I made no changes at all from the last time it ran.

Ether, or that staring fluid you used to spray into carbs. The revs will increase if it gets sucked into a leak.

Hmm.. sounds like a neat trick.. we would have to get it to stop hunting for idle and racing sitting there too for that to work..

D, no worry on the spacer, could be the problem as it seems to be a bit of a flakey piece anyhow.

What is the jet worth?

Five big ones. You owe me man.

Yeah, i'm not sure you can even purchase ether any more, but they do sell similar stuff that works the same. On a car it will only get you in the general area, but thats good enough as you can start really looking in that spot.
On these bikes I would imagine you could pinpoint it pretty accuratly.

Yikes, I might go bankrupt. :P

As a point of interest (for me anyway), my son's 1980 XR200 has a Keihin 30mm carb that is identical to the Mikuni in almost every way. There are some subtle manufacturing differences, but they're obviously spec'd for the same application.

Knowing that, I took the bowl off of the Keihin today, and found a 108 main jet inside. My recommendation to anyone that is installing a Mikuni on a Beast is to start at that level and work your way up, depending upon stock vs. performance exhaust and air filter.

I intend to install a 110 on T's Beast this weekend, so we'll see how it performs.

If you are not "happy" spraying starting fluid at hot running engines, you can try an un-lit propane torch, propane being less flammable than either.

Meh...I've been spraying that crap on hot running engines for 30 years to find vacuum leaks. Never had combustion yet, but I suppsose it could happen. I dont know the flash points of ether vs propane but the propane torch isnt a bad idea really. Everyones got one kicking around so it may save a trip to the store.

Sure, I've got a fire extinguisher.

One day I'll get so frustrated that I'll try and burn it to the frame...and out of sheer spite it probably wont burn.

Imagine the lovely smoke from the camo / orange / whatever plastic. I'll bet I could see it from my house.

Weldandgrind, can you tell me how much you got the performance exhaust for your 125cc for. John has them on back order, so it will be coming soon.