Anyone have any tips to get the bog out of the bottom end of my engine?

It's an LRP Z.28R Spec 3 in an Associated MGT. I have the high end figured out and it flies but it bogs pretty badly when coming off of idle. I tried leaning it out ~1/8-1/4 of a turn on the low/mid needle and it started not being able to hold an idle, went the other direction and the bogging just got even worse.

I am running 20% Traxxas Top Fuel with the stock gearing, and as I said earlier, once it is moving it just flies, but down low it is just annoying.

I have about a gallon on the engine, it still has an insane amount of pinch, and when I take the temp it hovers around the 210 degree range.


Any help is appreciated.

lean the low speed and richen the idle. Might try the nitro section of the forum.

I get what you are saying, and I think that will work, it sucks that it only has two needles (high, and mid/low).

I'll try that tomorrow, see how it goes.

ok keep us posted.

I forgot a screw backed out of the steering while I was running it last, looks like it will have to wait until next weekend when I get the screw kit in.

thats to bad

Also, does anyone know what size the hubs are?
I.e. 22mm, 17mm, etc., I just want to know for when I go to get better tires/wheels.

17mm

Have you done a pinch or temp drop test to check your low speed setting? Most folks seem to prefer the pinch test, but I've found that only gets it in the ball park and some engines need to be closer than the pinch test will get them. If you want the best low speed setting a temp drop test is the way to go.

It's been a while since I tuned an LRP BB, but I seem to remember it having a spraybar adjustment in addition to the LS and HS needles. A spraybar out of whack can cause the same thing you are describing. If it does have a spraybar adjustment, it's kind of a PITA to get it set right if it's been moved from it's default since it's most likely been set at the factory with a flow meter so the default position is slightly different on every engine.

Also, remember that the idle speed screw is always the last adjustment you make. If it's set wrong it would cause your engine to die when you are getting close to right on the low side. Use your throttle trim to hold the engine at a slightly high idle if you are having problems with the engine dying when you adjust the low side. Once you get the low speed set right, return your trim to it's original position and set your idle speed using idle speed screw.

I wrote this for the MGT a while back. Your MGT should really rip with a LRP engine in there...........

Most important speed tips for MGT

1. Use FOC (forward only conversion)
2. Get lighter tires and wheels
3. Tune the clutch
4. Tune your engine for power
5. Use 30% fuel
6. Experiment with gearing, 17/49 is good start with smaller tires
7. Make sure air filter is clean and flows well
8. Check carb linkage and be sure carb is opening all the way
9. Roll-out the truck on ground (by hand), make sure nothing is dragging
10. Tighten your slipper all the way, then just drive a little smoother
11. Consider a new engine, like the LRP Spec 3

If you do those things, your MGT will pretty much keep up with just about any truck out there.



Secrets to Wheelies and mean hole shots - If you wanna wheelie, check these items:

1. Tune the clutch - this is perhaps the most important thing to do! Use heavier springs - 1.1
2. Make sure the clutch is squeaky clean
3. Check the "Speed tips" above, but you won't need FOC to wheelie
4. Stiffen the rear suspension, heavier shock oil & springs
5. Double check to make sure your wheel hexes aren't stripped out
6. Tune HSN for good power, then perform "pinch test" to make sure low end (LSN) is set for good punch off the line. Pinch test means run engine, do a few high speed passes, then pull truck in and pinch fuel line with your fingers - close to carb. If engine dies immediately, LSN is too lean. If engine takes 5 or 6 seconds to dies then LSN is too rich. Engine should run for about 2 or 3 seconds, then speed up a tad, then die, then LSN is close to optimal.

1) Am waiting for it to arrive, but I stripped a drive cup screw (rear driveshaft), have to drill it out and get a new one.
2) Pro-Line Bow-Tie's, MTR
3) Clutch suits me well.
4) Figured out the tune.
5) Probably will switch to it Sunday, might need another head shim.
6) Stock works very well for me.
7) Brand new one in now.
8) Check it very often.
9) Diffs are grinding very little, can't do much about it.
10) Spur is almost always set as tight as possible.
11) Loving the LRP.



If it wasn't for the screw stripping out, I would be a very happy guy right now, but I have to go and get a carbide bit to drill it out.