Os 18tm no low end power

[Dirty-_-donkey]

Hey guys I have a os 18tm on my 2.5 Revo it runs great on the top end can hang with my buddy and his savy 4.6 my problem is off the line, when I gun it it bogs down for couple seconds before it rips loose. I have done everything I can think of tuning wise hsn lsn, mixture I try not to touch. I can't pull any wheelies, occasionally I get one in the grass but nothing to write home about.
I replaced all o rings on the needles got some of that green slime on top of that, all rand new slipper clutch, changed shock oil, added diff oil from an back and tightened my preloads and still nothing. when I turn the motor over with flywheel an plug in it is harder to turn then my buddy's 4.6 and he can't keep front end on the ground. However I took the head off and turned it over don't feel it get tight then, do I need a new pinch? Any help would be appreciated. Also I can replace sleeve piston and bearing for under $90 should I do that or spring for the picco?

Like I said though top end it gets it pretty good, is that just because it warms up an expands so its tighter? Sorry for the noobiness. Was going to seal motor but back plate screw is stripped and couldn't get carb out didn't want to break it. Figure easy out should get that screw out need to go get one and see if I can. Also suggestion for getting carb out would be helpfully too! Thanks in advance!

 

[Rolex]

You need to start leaning the LSN. Just a little at a time. Watch the temps.

 

[Pope]

Do it one hour at a time. When at idle your temp should be dropping a degree every few seconds if not you leaned it to much.

 

[Dirty-_-donkey]

Should running temp jump up when I lean out lsn? I set hsn first then when I try to set lsn it throws off my high speed temps. Even if I take lsn in till it want to start crawling on me an then back it off a tad I still don't get any power. When I do hit the breaks the motor will go right down to idle it doesn't stay revving high an slowly come back down. Shouldn't it wind down a little? Or is right to idle okay? Thanks for quick responses you guys are on top of your game

 

[Pope]

First make sure your linkage is keeping a little closed pressure on the carb slide when at idle and that under WOT it is opening the carb all the way.

Set you idle gap to about 1/2-1 mm. You won't touch this anymore after that. (edit) During HSN tuning till you adjust LSN.

Reset needles to factory. Always make adjustments 1 hour at a time on the needles.

Start it up and get it up to temp. Than pull a few WOT passes. When you let go of the gas the rpms should drop down right away and smoothly. Keep leaning the HSN till the RPMs start to hang up for a split second after you let off the gas. At that point back off the HSN till it no longer hangs up after a WOT pass and go richer 1-2 hours more past that.

Now for the LSN. You want to adjust this 1 hour at a time till your idle is smooth. After a WOT pass if the RPM's drop down than pick back up you are to lean on the LSN if the RPM's drop down and than it starts to bog down at idle the LSN is to rich.

You want a nice smooth idle and as low of rpms as you can get while still having the pick up. Remember even under a perfect tune the engine will load up with fuel when at idle and response will be slow if it has sat at idle for a few seconds.

At this point your temps should be right on and you should be seeing the temps drop while at idle.

 

[Dirty-_-donkey]

Thanks pope, I've been tunin this thing for 3 weeks now lol. My carb doesn't open all the way at wot, didn't know whether it should or not just figured what it is, is what it is. and I'll recheck idle screw position. I'll have to figure out how to get carb fully open. Thanks guys

 

[Pope]

Linkage and end point adjustments and subtrims.

 

[Dirty-_-donkey]

I did upgrade to the 2.4 radio and waterproof servos so I should be able to do end points with that correct? And I can fiddle with linkage to. Bout to have machinist at work get stripped screw out so I can seal backplate. Any advice for carb? Should that just pop out when I loosen screw? Thanks you

 

[Pope]

They can be hard some times.

 

[Extreme RC Mods]

Follow this tuning guide word for word and the engine will be tuned "just" on the safe side of a perfect tune, given there are no issues with it.

http://www.extremercmods.com/content/tuning-popup.html

 

[Dirty-_-donkey]

Thanks, we did get stripped screw out so will be sealing motor tonight, and will follow that guide. Thanks guys

 

[Zdragon71]

+1 That link to tuning is what I've followed and it is dead on everytime. I've got it saved in my bookmarks for reference.

 

[Dirty-_-donkey]

Thanks everyone my idle gap was pretty small, explained why I had to take lsn in so much, naturally ran out of nitro before could start tuning it up from there, I'll post how it goes tomorrow.

 

[Dirty-_-donkey]

Once again thanks guys! Its a brand new beast! Since when I was looking for Answere I didn't find a thread that actually concluded their results here's what I learned and worked for me.

- set carb to factory needle settings with 1mm idle gap
- set idle to decent idle
- set hsn
- set lsn
- readjusted idle
Hopefully that helps someone in the future the above link from extremercmods was very helpfully as well. Still have some adjustments to make but I'm on the right track now and actually pulled wheelie on asphalt!

 

[Rolex]

Set you idle gap to about 1/2-1 mm. You won't touch this anymore after that.

Wrong information. That's the approximate starting point, just like resetting the needles to factory. When you tune the LSN, the idle has to be adjusted accordingly to compensate for the change in RPMs.
When the LSN is leaned the idle will increase. You're telling him not to touch the idle screw again for any reason.
Following your advise means that the car will start to crawl forward as the LSN reaches its best setting, but he should not adjust it? Explain.

 

[Extreme RC Mods]

The idle gap should be set and then not touched, from there you will adjust the LSN for the idle. The link below explains the procedure in detail, too bad it and the tuning guide aren't stickied in the engines section so it's more easy for people to find and read, it's helped hundreds if not thousands of people already.

https://www.rcnitrotalk.com/forum/showthread.php?t=94326

 

[Pope]

I am sorry. You are right. I meant during the high speed needle setting.

I corrected post. Thank you for catching that.

 

[Ericehess]

Once again thanks guys! Its a brand new beast! Since when I was looking for Answere I didn't find a thread that actually concluded their results here's what I learned and worked for me.

- set carb to factory needle settings with 1mm idle gap
- set idle to decent idle
- set hsn
- set lsn
- readjusted idle
Hopefully that helps someone in the future the above link from extremercmods was very helpfully as well. Still have some adjustments to make but I'm on the right track now and actually pulled wheelie on asphalt!

I dont know much about gad RC but your pinion gear could be too big. Could try dropping it down a couple teeth..should give you better low end power but will decrease top end slightly.

 

[olds97_lss]

I dont know much about gad RC but your pinion gear could be too big. Could try dropping it down a couple teeth..should give you better low end power but will decrease top end slightly.

This is an 8 year old thread. If he hasn't sorted it out by now... he may have other issues.