tuning

[Dickylew]

hi all, got a Hobao Hyper 7 black around xmas time and need advice on tuning the engine.

Ive started to lean it out a bit but after running about 5 minutes the engine cuts out.
I notice at the top of the glow its fizzing with fuel slightly and the engine seems to be a bit lumpy but not too bad at full throttle.

Would this indicate that it is running too rich?

Where should i start? leaning the main throttle or the low speed throttle first, bit concerned as im still learning and dont want to risk overheating the engine by running too lean.

Any advice would be appreciated.

[gramey]

Stupid question but have you had the glow plug out and if so made sure you put the copper washer back when replacing it? It shouldn't really be fizzing with fuel. Also if you've had the glow in and out several times whilst breaking the engine in the washer may have become hard and compressed so not sealing the plug properly.
Did you get a manual with it as it should explain in there how best to set it up and where approximately you should end up with a fully run in engine, i.e. factory setting is 3 1/2 turns out and once broken in should be in the area of 2 1/2 turns or similar.
Try and find the factory default settings for your engine as this will give you a base setting to return to if you get stuck.
Personally I would suggest setting your idle up first so that the car will happily tick over for about 30 - 40 seconds without stalling. Then gently accelerate the car and run it round for a bit to clear any excess fuel and then give it a short burst of full throttle. If it's coughing and spluttering, or appears to be holding back, whilst at full throttle it's more than likely running too rich and you need to adjust the HSN 1/8 of a turn at a time to get it nice and crisp.
If it's screaming it's head off at full throttle and there's no smoke coming from the exhaust it's too lean. You should have a thin trail of smoke coming from it when at full throttle.
Then you can adjust your mid range so that you get a nice smooth pull away from tick over, if it bogs down when you go to accelerate from a standstill after about 20 secs of ticking over it's too rich and if it doesn't drop down to a nice smooth tickover but holds the revs up when you release the throttle it's too lean (mid range needle).
I would recommend not altering any of your settings by more than a 1/4 of a turn at a time and it may well be 1/8th of a turn will be sufficient.
I only race at club level so hopefully one of the big boy's of the sport will read this and may be able to offer more/better help.

[Dickylew]

Hi thanks for the advice, took the car out today got it runnung and seem ed to run ok for a while but engine stalled when left to idle.

I checked the glow plug and it was blackened and a bit wet it was a new plug and it failed just after one run.

This car at low speed runs very lumpy like a 4 cylinder car miss-firing cant seem to get it smooth.

I took it home and had a fiddle with the settings, this car has never been easy to start but i turned up the idle screw and it started much easier.

However it now cuts out when i blip the throttle.

I have taken your advice now and have reset the factory settings to give me a starting point,next weekend will try again from scratch and slowly lean it out and see how it goes..

Thanks for the advise.

[gramey]

If it's cutting out whe you blip the throttle your mid range needs adjusting, I would suggest a touch leaner as it should pick up nice and quickly. If it gets to the stage where it's hanging up on the throttle, i.e. when you shut the throttel it doesn't come down to a tick over almost straight away, you've gone too lean.

[Driftwood]

Hi. Are you new to nitro buggies like me? I wonder if you did what I did. I decided to "fiddle" with the carb when I first got mine and as per instructions wound the low speed needle valve in till it stopped and then wound it out the correct number of turns. It was a pig to start after this. It struggled to pull but seemed ok when the revs got up. It wouldn't idle for long and sometimes stalled when whacking the throttle open. It ate glow plugs.
I discovered that I wound the needle in too far. Even with minimal force, it went in so far in that it opened the throttle and that the needle was so far in it probably blocked the jet until full throttle was used.
To get the correct setting I wound the needle all the way out and held the throttle shut using light pressure on the servo link and looked down the carb' to make sure. Then I carefully wound the needle back in till I felt it stop and cheked the throttle still hit the idle stop when closed. This is my start point for setting the carb'.
It could be that being new to nitro power I was "ham-fisted" during my initial "fiddling" and you are not, but I would check this anyway. Correcting my mistake solved my problems instantly, and restored my sanity after spending ages trying to get it started and running right.

[Dickylew]

Hi first chance ive had to get back to the forum.

Thanks again for your reply.
Yes i am new to nitro just starting to understand how things work, i will take onboard regarding winding the setting screw in too far.

This weekend i will start from factory settings, think ill start with the idle screw and try to get a smooth tickover; then ill run the car and slowly lean out the main screw until runs ok.

Ill let you know how i get on.