MBX5/OS VZ-R troubles!!

[HeartBreak]

Okay, I'm about to pull my hair out on this one. I've searched the forum until almost going cross-eyed, and can't find anything to help explain what I'm going through...

I have an MBX5 Prospec buggy with an OS VZ-R II engine in it. Did the break-in, up to the point where I can pull full throttle. This is where the pain begins.

Engine runs perfect for roughly about 10-20 seconds, then it starts to heat up FAST. Hits 270F+ at idle. Yes, IDLE. Needle settings are flush on all, idle air opening is set to allow the motor to run without the clutch engaging. You know, standard fare. This is all sitting on the starter box, wheels off ground, brakes not dragging at all.

Now, here's where the fun begins... A pull on the throttle usually causes the motor to die at around 1/3rd throttle. Leaning it about 1/8th of a turn allows me to get more throttle. Eventually, I can get it to reach full throttle, but that's only with a glow plug lighter attached. Temps approach 310F at this point. Without the glow lighter attached, engine cuts off suddenly.

With the glow lighter attached, the engine stutters, like it's bumping itself over. It also revvs high (sounds like a woodpecker) when returned to idle.

During all of this, lots of blue smoke and spittle from the exhaust.

It has a P7 plug in it, and is being ran on 20% Trinity. I'm also aware that because of the excessive heat, the bearings are probably fubar'd.

Ideas?!

Any help would be appriciated; otherwise this motor is going to meet its maker, in the form of a 10 pound sledgehammer, and mailed back to OS with a rather 'nice' letter.

 

[Monkey Wrench]

HB, I'm assuming you checked the normal culprits (sealed the carb and backplate, checked the fuel lines for holes, made sure the fuel filter is tight, etc.)? Only other thing I can think of, off the top of my head, is that the carb gaskets might be torn. 270 at idle, huh? Man, that is a tad on the warm side!

 

[hamz9561]

I'd double check the carb and backplate sealing. I'd also set it back to the factory settings. These are the obvious steps. Then I'd follow the Monkey man's advice.

 

[ImBroken]

The woodpecker sound at idle doesn't sound right at all.. Are you sure the P7 plug isnt too long? Is that mill you have a Turbo, cause that's a long plug..
From what I see, if this is the same mill, it's really designed for an 1/8th scale onroad car. That shouldn't make any difference in the way it's running, but something to think about. Good luck..
http://images.google.com/imgres?img...firefox-a&rls=org.mozilla:en-US:official&sa=N

 

[tinman4009]

sounds like the low speed is lean and high speed is rich ??

 

[Buggyracer28]

Yeah, i would think the low is too lean, and the high isnt getting enough attention. There might also be a leak somewhere, or even a plug issue like said before.

 

[HeartBreak]

I've put all new lines on it (tried well over 10 feet total of fuel line). Also went through the fun of rebuilding the carb from step-one. All the needles, except the high needle, felt a little "loose" when turned. I put new o-rings on all of them, even the neck of the carb, and no difference.

The plug that it came with is a P7; even recommends it in the manual. I've made sure that all surfaces are clean and sealed.

Even went through the exhaust pipe and checked for leaks.

The one thing that I did notice, and I find rather odd, is that at full throttle, the low needle will not clear the spray bar.

I know the motors' designed for an onroad car; I meant to order the VZ-B, but the rep at tower mis-heard me. I'm lucky that I got the MBX5 and not some airplane by mistake, lol.

I'm honestly thinking about just yanking this s-o-b and putting a non-OS motor in my buggy.

 

[HeartBreak]

Update: I GOT IT FIXED!!!!!!!!!!!!!!!!!!!!!!!!!!!

The middle mid-range o-ring was too small of a diameter!!!!! I replaced it with an extra o-ring from another carb's low needle, and that fixed it.

That, and it was a FULL TURN TOO LEAN! Picture of the setting to follow, but I just ran it, and it ran AWESOME at 235F!!! Man, I am stoked!!! Thanks to all that helped me on this one.

Keep in mind, the other needles are; high end is at 2.3 turns from closed (give or take) and the low end is flush. Idle is set to factory settings (.5mm).

 

[jetmechG550]

Never saw a mid range needle stick out so far.

 

[HeartBreak]

Yeah, that's what's tripping me up... But I was able to run it up to full throttle and have it idle flawlessly. I tell ya, these OS motors... I don't think I'll be buying another one. This is the second one that I've had in a row that's come from the factory with a messed up carb.

 

[jetmechG550]

I have two V-specs and have had zero issues. They are easy to tune and seem to hold one for me just fine.

 

[HeartBreak]

I must have gotten two lemons. But it seems unlikely, don'tcha think? When you really take it at face value, the problems were o-rings, and not the actual engine itself. I really can't hold OS accountable, but I would like to know just how stringent their quality control department is.

 

[Monkey Wrench]

Resist...temptation...pink....fuel...won't...say...anything...lines....pink...

 

[HeartBreak]

LOL. Jealous, monkey? :whistle: