Alternate carb for a LRP 28 S3

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olds97_lss

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Anyone know of alternate carbs that work well in an LRP 28 S3? I'm really fighting with one of my LRP's and am getting really frustrated with it.

I know there are no air leaks (fully torn down and sealed back up) and it seems relatively responsive to tune, but it seems that I have to run it at least 1.5-2 turns rich beyond factory to get it to run anywhere near right. Even then I get the indicative high idle after a high speed pass and the occasional lean bog if I gun the throttle. The power is lacking, except for the occasional half second that it sounds like it's running right and temps are average above 250F. Have tried multiple pipes, changed plugs, sealed everything, new ceramic bearings, fresh fuel, different fuel tank and new lines...

The one in my aftershock runs like a top, but I'd really like to run my savage. I tried the Losi HT pipe on it and still no good, which I'm running on my aftershock.

Did I just get a full on defective LRP?!?!? Very reminiscent of the axial paper weight I bought many years ago...

My post about changing out the bearings trying to eliminate my issues:
https://www.rcnitrotalk.com/forum/showthread.php?t=83557

No luck there...
 
If it's the same size as a z28 carb then a losi 454 carb should fit.
 
IF the Losi 454 is in fact a clone of the LRP 28S3, the Dynamite .28 carb, and the 454 carb should work. I have the 454, and there was no tuning issues, with the exception of a leaky fuel tank.

Now I am reading that the neck on the LRP is smaller. So don't hold me to this. :)
 
Would be nice if mfr's listed the neck dimensions of carbs online...

I kind of post whored this in a few of the main forums I visit, since LRP was big with many MT's, figured the most exposure to my question would yield more results.

Some say the LRP and 454 have issues like mine and that it's the carb. Others say theirs works great. Right now, I'm 50/50 with one working good and the other not. So, now I just have to figure out if buying a $40 replacement LRP carb is the way I want to go, to make it either 33% failure or 66% failure... or unless someone knows more about what carbs work.
 
have you tried the one from your good working engine on it ....it would let you know if its your carb that is the problem ..or if its your engine that is just bad ...thats what i would do ;)

just a thought ;)
 
Yep, thought the same thing. Was trying to avoid that by doing everything else first. Since I really don't drive the aftershock much... or ever, I almost tore the entire engine out of it and put it in the savage today while in the midst of my frustration... but I refrained.

Supposed to rain off and on all weekend, but I may swap it out tomorrow night and try it in between showers on Sunday. Then at least I'll know if it's worth to gambling with spending $40 for a new carb.
 
thats what i would do before spending $$$ ;) that way youll know if its a carb problem or not ;) ....i have 2 trucks and 4 spare engines ..lol...if one doesn't run right , i swap it ...lol :D
 
I know this is an old thread, but it's mine and I'm still fighting with this engine. If I had remembered this thread, I probably would have just removed the engine and got a new one, considering it's been 6 years and the engine is still flaky. Guess I have a hard time giving up on an LRP...

Tried the 454 carb, ran better, but still flaky. I'm trying a lowered stock tank mod to help with the HTL issue as well.

The symptoms are indicative of a bad tune. Won't idle well without stalling, sounds fat half the time and lean the other half. Today with the new 454 installed is the best it's ran so far. I tuned the carb per losi's manual (2.5 turns out from closed on both needles), but it was waaaaaay too lean. It's probably closer to 4 turns out for both at this point. Temps seem fairly stable, 230-260 range. Power is decent through the RPM range with an occasional rich bog in the middle. The only real issues that remain are the inability to idle for long without stalling and the high RPM whine/lean sound after a short WOT run. If I blip the throttle a bit after a WOT run, the engine calms down right away, but if I jsut let off the gas and coast, the high rpm/lean sound lasts for a few seconds.

I want to richen the LSN more, but then it bogs excessively off the line after a few seconds of idle and likes to die. As it is, the idle screw doesn't help things much.

Just frustrating... I'm 99% sure I'm going to pull the LRP out of a buggy I never drive and swap them. I know it ran good, it was just the oldest LRP I had with the most fuel through it. I put it into a buggy that I knew I wouldn't drive much and just wanted something reliable in it for the few occasions I took it off the shelf.
 
Every once in a while you're going to get something that isn't right from a given manufacturer, @olds97_lss. It's just the nature of the beast. I was told when I was selling consumer electronics that you can expect up to 10% of any product to have a flaw of some kind out of the box. It sounds like this one was destined to be a paperweight. You did due diligence to get it running.
 
Was hoping I could buck the curve, but I guess not. Will have more time later this week to tear it down and swap engines with my buggy so I can get some wheel time at least without ripping what hair I do have left, out.
 
I err'd on the side of knee jerk and just ordered a new LRP ZR.30 for $170 shipped on ebay. Hopefully it will show up before the weekend and I'll get the fun task of breaking in a new engine... Not looking forward to that. The 28's were tough on my fingers during break-in.

Sucks though that the LRP28 gave me such headaches. Only has a couple gallons on it. I guess it will be good for parts for the other two I still have. I'll still give it a good once over to see if I see any seepage anywhere when I replace it.
 
I err'd on the side of knee jerk and just ordered a new LRP ZR.30 for $170 shipped on ebay. Hopefully it will show up before the weekend and I'll get the fun task of breaking in a new engine... Not looking forward to that. The 28's were tough on my fingers during break-in.

Sucks though that the LRP28 gave me such headaches. Only has a couple gallons on it. I guess it will be good for parts for the other two I still have. I'll still give it a good once over to see if I see any seepage anywhere when I replace it.

Check for Carnuba Wax residue, @olds97_lss. @Rolex has been on a waxing tear again the batcave. The tuba had 2 in. layer of the stuff...
 
Keep us updated olds. As I'm kinda at the same stage as you with my 32 I'd like to see how you get on
 
Keep us updated olds. As I'm kinda at the same stage as you with my 32 I'd like to see how you get on
Well, I gave up. Other than giving it a once over as I take it out to throw it in a drawer, there's nothing much left I can do to it. Maybe some day when one of my other 28's wears out/loses pinch, I'll pull the sleeve/piston and try it in another engine. Considering how much I run, it will be years before I wear out the LRP's I already have.
 
I just finished tearing the engine down. Figured why wait. I took high res photo's of every angle of it as I took it apart and I don't see any evidence of a leak or any cracks. All the milling inside the crankcase looks ok too, nice clean edges to all the cuts, no burrs to speak of. At first, when I rotated the crank with the head off, I didn't feel any pinch, so thought maybe it prematurely wore out and that was the issue. After getting it apart and manually pushing the piston in the sleeve, it doesn't go much over 3/4 the way up the sleeve before it requires a lot of force. So, not that either. Also no slop in the con-rod or strange markings on the piston.

So, nothing evident. New carb, new bearings, fully sealed with RTV, twice. No visible leaks or cracks. Still ran like crap.
 
I just finished tearing the engine down. Figured why wait. I took high res photo's of every angle of it as I took it apart and I don't see any evidence of a leak or any cracks. All the milling inside the crankcase looks ok too, nice clean edges to all the cuts, no burrs to speak of. At first, when I rotated the crank with the head off, I didn't feel any pinch, so thought maybe it prematurely wore out and that was the issue. After getting it apart and manually pushing the piston in the sleeve, it doesn't go much over 3/4 the way up the sleeve before it requires a lot of force. So, not that either. Also no slop in the con-rod or strange markings on the piston.

So, nothing evident. New carb, new bearings, fully sealed with RTV, twice. No visible leaks or cracks. Still ran like crap.

Does it have one of those plastic or composit carb bodies?
 
Does it have one of those plastic or composit carb bodies?
No. The LRP carb is painted with the HSN end unpainted, but it's solid. The second Losi 454 carb is not painted and is also solid.

The picco in my drawer that I didn't use yet has one of those half and half carbs. I know they can tend to cause issues once heated. That's kind of the reason I didn't just use that engine vs buying a new one... I learned about the likely carb issue after I bought it and I never broke it in.

I had an old omega engine that had one of those carbs. It ran awful after a short while.
 
I had a thought last night as I was laying in bed staring at the ceiling waiting for sleep... I wonder if the filter in the tank is clogged. Originally, I had an old OFNA 125cc buggy tank in it because of the HTL issue with the stock tank. At the end of last year, that's the tank I ran and it was leaking all over out of the cap due to a tired spring, worn o-ring. The tank has been discontinued, so I can't find a new one. So, I put in the original tank that has been sitting in a drawer for 3 years and lowered it about 3/4" as suggested by someone to combat the HTL issue.

If the filter was partially clogged, it would idle fine (which it does for the most part), but would starve for fuel as the RPM's went up, which it seemed to be doing. I kept adjusting the HSN to try to get the "lean bog" when punching the gas to go away and to get the temps down below 270F. I was way over rich on the HSN by more than a turn over factory. Then the idle was so blubbery that it wanted to constantly stall. Even with the HSN way rich, it still ran hot and would still have the off throttle lean rev that I couldn't get to tune out.

It's supposed to be a tad on the cool side this weekend for break-in, so I suppose I could put the 28 back together and back in the truck with the new X tank I have sitting on a shelf that I ordered and didn't install because I found my tank.

Not sure how to test a tank for fuel flow other than trying a different tank. The stock tanks do have a stone filter in them, right? I did run 5 or so tanks of fuel through it, so one could assume that if it was partially clogged with old fuel/oil that it would have dissolved by now and this isn't my issue. But maybe not...
 
I believe mine has a stone filter. Before I broke the old one in a crash, I used a can of Heet to un-gum it. Methyl Alcohol essentially. That may be an issue.
 

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