hksmonaro

hey guys,

Wondering if I could get some help with my Nitro buggy 1/8th. Ive had it for about 7 years and never really had an issue with it and only really used it on and off (never had to adjust anything other than the high speed needle), approx. 5 litre of 16% nitro run through it total. Still has compression cold and warm.

It starts fine cold, idles while cool. If I then start using it and get it up to operating temp it responds and runs ok, but it I slam on the breaks hardish or slow to a roll then stop it will stall. Same thing happens if I have it on a block and accelerate then break, it stops. I'd adjusted the idle gab, it was just under 1mm. Screwed it in clock wise to increase the gap to around 1mm, this didn't help. Only if I make the gap massive it will stay running when breaking hard, it still 'may' stall at times but not consistently.

Ive pulled the clutch apart and seems ok, how can I tell if it is worn. I dont think he clutch is engaging too early.

Ive cleaned out the carby/engine well and that has helped with it running better but still stalling on braking?

Any ideas?



Ive got not idea what model this engine is or size. Bought it cheap on eBay for 278 delivered!

1QwkSport2.5r

Usually a broken clutch spring can cause the engine to quit when you apply the brakes. You've already tried opening the idle gap which didn't help (and for reference, 1mm idle gap is too much - .5-.7mm is better). Check the clutch springs and make sure they're not too worn or one is broken.

hksmonaro

ok cool thanks for the info, I'll turn back the idle little from the 1mm mark to .5 - .7 or so.

How can I tell if the springs are too worn? All three sections of the clutch have the same amount of tension if I put a flat head screw drive in the slightly flex them out? is there another test I can do>?

Also, how can I determine what the 'default' LSN adjustment is? From what Ive read though that shouldn't really affect the idle much, its more from low to mid range acceleration yeah?

1QwkSport2.5r

The base setting for the low speed mixture needle is usually flush with the end of the throttle valve (usually about 1/4-1/2 turn leaner from flush with the outside of the throttle arm. As for the clutch shoes/springs - if the springs are shiny at all (it appears yours are black) or if they are blued at all, the shoes are too worn and that would cause the springs to lose some tension and engage the clutch too soon. If a clutch spring is broken, it could cause one shoe to engage at idle and stopping the car would put enough drag on the engine to stop it. If the springs aren't broken and no showing wear, then I'd be looking at the throttle linkage and the needle settings to ensure the throttle valve isn't closing too much under braking and the mixture isn't too lean.

Closing the idle gap will lean your idle mixture, so perhaps setting your mixture needles a fair bit fatter and "starting over" may be in order of the clutch is indeed up to snuff.

1QwkSport2.5r

Could you post a video of what the engine/car is doing?

hksmonaro

awesome thanks will give those things a crack, yep I'll go give it a run and post a video! Also something to note is when it is hot and and I have to restart it it can be a pain to get going again, sometimes I have to have the throttle 1/4 or 1/2 to get it to start again, not sure if thats helpful.

The section of the clutch that touches the inner bell housing is very shiny compared to the rest of the clutch material.

cheers

1QwkSport2.5r

The first part of your reply tells me your idle mixture is too rich - likely because your idle gap was too big. The second part of your reply sounds normal. As long as the springs aren't wearing on the inside of the clutchbell, then it sounds like your problem is due to fuel mixture and not the clutch/clutchbell. Too rich of a mixture and too wide of a gap can require an over-lean main needle setting causing a compensation of sorts between the needles. Getting the idle gap narrower and dialing in the needles properly will give better performance and help the engine last longer. Set your high speed rich as well as the idle mix and then set your main needle first to peak power or just rich of peak, then set the idle mix for good throttle response to WOT and the engine only being slightly loaded up after a 15-20 second idle.

hksmonaro

Ok cool, Ive set back the idle gap now see pictures and video's below. Please feel free to provide any pointers on what I may be doing wrong also

Video (Click Here) is startup from cold, I think it is starting ok and getting it warm very rich too. Need to use some throttle to get it too start, still having issues idling. During initial idle is that considering standard idle RPM? if it is that would mean the clutch is stuffed yeah?
Video (Click Here) is the engine warmish and dialings in the HSN, had fuel spewing out the exhaust but adjustment helped that. Also shows idle gap when it stalls. The LSN is flush with the outer 'housing' of the truttle arm thing.
Video (Click Here) is at operating temp, able to start it with extra throttle but still not idling. Just stalls now even with no real braking applied.

Picture here shows the idle gap, full brake engagement does not close the gap during tests.

hksmonaro

just watched a few other videos of models similar and they are idling a bit high then mine and the wheels/clutch hasnt engaged yet. Is it possible to adjust the clutch?

hksmonaro

just removed the clutch bell housing and parts and still cannot get it too idle with anything less than like 2-3m of idle gap? so definitely not the clutch since its not even connected and getting the same issues.

1QwkSport2.5r

All three of your videos shows me the idle mixture is too rich. If you need to open the throttle to get it started, that tells me it's too rich on the low side. Lean the idle mixture a little at a time (1/16 turn) until it will start and stay running without adding throttle to do it. Once it will start and run/idle on its own, warm it up well and set the high speed needle so it's revving cleanly. Then finish adjusting the idle needle so it will idle for 10-15 seconds (without dying) and when you punch it to WOT it's only a little loaded up. Maybe just a slight burble before it cleans out and winds up. Do all of this with the car on the ground and not on a block.

hksmonaro

Hi, i tried what you suggested a few times. Different combinations, doing 1/16 to /18th turns slowly in and testing after each adjustment. I cannot get it too idle. Basically does the same thing in third video. The closest I got was idling for like 4 seconds but still high enough for the wheels to keep spinning. Starting it doesnt work unless I apply a bit of throttle too. Any other sugestions? Vacuum leaks? worn needles? fuel starvation issue?

1QwkSport2.5r

Try a new glow plug? Maybe a hotter one? What fuel and plugs are you using now?

hksmonaro

hey mate, just checked a few things. So the original plugs is a SH N4, the new plug I bought (after the issues started) is an OS 8, I believe both plugs are 'medium' heat style of plug is that correct? Also using 16% Nitro mixture fuel. Does the heat required from the plug increase as the engine gets older/worn?

I completely pulled apart the carby today and cleaned all the needles/rubbers ec ec to check for any blockage/breaks, all seems fine.

Re-tried the tuning process again and still the same result, can only get it to idle on like 2mm gap.

Here are some photos of the Carby parts.

Also when the car is tune correct and running normally, should I be able to start the engine without applying any throttle andq just start idling?

The engine did sit for a number of years, is there anything inside the engine that could be causing the issue? seals? rust? bearings or bushes?

and how can you tell if the piston/sleeve dont have the required amount of compression to run normally/idle or be tuned correctly? Ive read that a worn engine will start fine but when hot it will be really hard to start if at all as there is no compression in the engine anymore?

Thanks again

nic