Rovan Baja won't hold a tune

[RcJunkie13]

But, my engine starts up and runs fin for about 15 minutes and then goes super rich to the point where if you stop giving it throttle the engine will cut out.

Then don’t say it was richening

 

[Seandonato73]

Look bud, you need to work on it when you have some free time and a space to run it hard. You likely either have a carb issue, or a small air leak that your trying to tune out.

 

[KevTrem]

Can you do us a favour please and post some pics of your rig? Doesn't have to be running, just that way we may be able to spot something that hasn't been explained.

Do you notice before it dies if the revs start raising or falling as you try to idle? What settings do you have your needles set at? Is your engine stock? Have you checked your fuel tank is venting properly? Have you checked your engine to make sure its not packed with grass beneath the covers? Do you have the stock isolator or have you upgraded to an aluminium one? What spark plug are you running? Have you checked head bolts are tight? Have you checked the carb/isolator gaskets are sealed?

Next time your out grab some video footage of what its doing, upload to Youtube and copy the link to the forum so we can view it to try and help further.

 

[Polar_Bus]

Sounds like heat soak to me. Had that happen due to a billet isolator for the carb. Your boiling the liquid gas which in turn leans the engine since there's less liquid fuel and your carb wasn't designed to meter a gaseous fuel only liquid so thats why it's hard to tune when the engine is hot....whats it like when you try to start it when the engine is hot.... how long does it take to start

My 36cc Rovan uses a composite carb spacer but other Rovan models might use alloy . I'm pretty sure that weak compression will allow an engine to run but will cause higher running temps from lack of power and not completely efficiently burning the fuel mixture .

 

[Taken]

Can you do us a favour please and post some pics of your rig? Doesn't have to be running, just that way we may be able to spot something that hasn't been explained.

Do you notice before it dies if the revs start raising or falling as you try to idle? What settings do you have your needles set at? Is your engine stock? Have you checked your fuel tank is venting properly? Have you checked your engine to make sure its not packed with grass beneath the covers? Do you have the stock isolator or have you upgraded to an aluminium one? What spark plug are you running? Have you checked head bolts are tight? Have you checked the carb/isolator gaskets are sealed?

Next time your out grab some video footage of what its doing, upload to Youtube and copy the link to the forum so we can view it to try and help further.

I should be able to do a running video on sunday, but here are some pictures for now. The engine is stock, the fuel tank is venting, and if by isolator you mean the thing that goes between the carb and the engine, then yes it's plastic. I am running an NKG spark plug. I have run almost 30 tanks through this engine and there seems to be quite a lot of residue on the piston.

 

[KevTrem]

Thanks for the pics.

So from what I can see you air filter is not stopping dust and dirt from entering your engine, could also do with cleaning, oiling and an outerwear looking at pics.

Your idle screw screw is wound all the way in.

The rig looks like its in desperate need of some cleaning and if you've ran 30 tanks through that engine without having to change the ring then my guess is thats about due, you've put about 6 gallons of fuel through it.

 

[Taken]

Thanks for the pics.

So from what I can see you air filter is not stopping dust and dirt from entering your engine, could also do with cleaning, oiling and an outerwear looking at pics.

Your idle screw screw is wound all the way in.

The rig looks like its in desperate need of some cleaning and if you've ran 30 tanks through that engine without having to change the ring then my guess is thats about due, you've put about 6 gallons of fuel through it.

Ok thanks.

 

[Seandonato73]

Thanks for the pics.

So from what I can see you air filter is not stopping dust and dirt from entering your engine, could also do with cleaning, oiling and an outerwear looking at pics.

Your idle screw screw is wound all the way in.

The rig looks like its in desperate need of some cleaning and if you've ran 30 tanks through that engine without having to change the ring then my guess is thats about due, you've put about 6 gallons of fuel through it.

I pretty much concur with your assessment. Although by this point the op should notice a lack of power of its a ring issue.
Compression test will tell the tale of the ring.
The build up is from excessive oil, crap oil, and or excessively rich tune.
That old plug is less then worthless for checking tune. Needs done on new plug, with engine already to temp. Covered this many times already. Anyway. Stop looking at the plug it's worthless.
Either way your tuning is off as well. The idle screw sunk all the way or nearly all the way in means you have the low needle too rich, which could also mean your compensating for an air leak. I preach this all the time. Pressure and vacuum test to rule out leaks and bad seals. Compression test to check ring. I'd be surprised if all check out ok from the pictures you've provided.

 

[Taken]

I pretty much concur with your assessment. Although by this point the op should notice a lack of power of its a ring issue.
Compression test will tell the tale of the ring.
The build up is from excessive oil, crap oil, and or excessively rich tune.
That old plug is less then worthless for checking tune. Needs done on new plug, with engine already to temp. Covered this many times already. Anyway. Stop looking at the plug it's worthless.
Either way your tuning is off as well. The idle screw sunk all the way or nearly all the way in means you have the low needle too rich, which could also mean your compensating for an air leak. I preach this all the time. Pressure and vacuum test to rule out leaks and bad seals. Compression test to check ring. I'd be surprised if all check out ok from the pictures you've provided.

Ok, thanks for the advice. Is there a way to check if there is an air leak?

 

[Seandonato73]

Pressure and vac test. Basically block the carb and exhaust off, need a hole for a fitting in one of them, or make an adapter out of an old spark plug. 10-15 psi in it, make sure the transfers are open and look for leaks. Don't be afraid to dunk it in water to find the leak. All covers off and flywheel and clutch off. Vac test same thing but it's more to test the crank seals as they can leak under vac and not pressure or vice versa. The gaskets will show with the pressure test about 10 in hg for vac. Should hold pretty much solid for 5 min or so. A mity vac is what I use, but Amazon/evilbay sells knock offs for pretty reasonable prices.

 

[Rep732]

I can see you had some dust ingestion... been there and wasted a brand new engine. If I was you and seeing how filthy everything is id condem that engine

This is the proper way to "dust" an engine
https://www.largescaleforums.com/threads/bad-news-for-my-new-red-arrow-34cc-engine.26031/

 

[Polar_Bus]

Li

I should be able to do a running video on sunday, but here are some pictures for now. The engine is stock, the fuel tank is venting, and if by isolator you mean the thing that goes between the carb and the engine, then yes it's plastic. I am running an NKG spark plug. I have run almost 30 tanks through this engine and there seems to be quite a lot of residue on the piston.

The pic of the mud ingested carb venturi inlet tells me all I need to see. Sorry to be morbid, but your top end is junk, and your crank bearings are probably close to being junk. Your engine needs to come apart for an thorough inspection. Hopefully after dissasembly you can prove me wrong.

 

[Taken]

Li

The pic of the mud ingested carb venturi inlet tells me all I need to see. Sorry to be morbid, but your top end is junk, and your crank bearings are probably close to being junk. Your engine needs to come apart for an thorough inspection. Hopefully after dissasembly you can prove me wrong.

Ok I have some pictures of the inside of the engine, and the cylinder walls are quite scratched up and the piston has a few scratches and stains on it.

 

[Rep732]

Just a word of advise for next time, do not open up the engine with all of that dirt on it as it's going to fall inside the engine case. Do your best to use an air compressor to blow it all off with the exhaust and intake with the air filter still on it.

And yea your engine needs to be rebuilt those scratches are hurting performance and causing a bit of compression loss

 

[RcJunkie13]

Just tell Rovan that the filter (oiled properly) let dirt into the engine. He might give you a rebuild regardless of warranty

 

[Rep732]

This is what I think of clone engines

 

[KevTrem]

Just tell Rovan that the filter (oiled properly) let dirt into the engine. He might give you a rebuild regardless of warranty

After over 6 gallons of fuel I think he's due a rebuild anyways Junkie.

You can buy the 29cc top end rebuild kit for about £22, comes with piston, ring, c clips, gaskets and cylinder plus spark plug.

Take the top off the engine, flush the poop out with petrol, then rebuild.

Clean your air filter, oil it and bang an outerwear on it, Rovan even make the outerwear for that filter.

Go give it a run, to be honest 6 gallons of fuel through those engines is good going and they are cheap as fook to keep rebuilding and its experience before you step up to more expensive engines. I've been there and it's fun.
You need to up you maintenance schedule though, clean it down after every run, doesn't have to be spotless but that amount of dust and dirt you've pictured isn't helping your rig and will be wearing stuff out quicker.

 

[Mick Boomer]

Anytime theres oily gunked up poop built up that’s always a tattletale sign of a leak.

 

[DAVE1979SK]

you can have the best air filter you can buy. but if it is not regularly cleaned and oiled, the engine will turn out exactly like yours I see in the pictures. I see you're neglecting maintenance and just ride . this is not how it works in 1/5 gas rc . it depends on whether you take the hobby a little serious or you ride just for "fun". It depends on you ...

 

[Taken]

Well I went to get some running footage today and it wouldn't start. So I'm guessing whatever is causing the tuning problem has completely broken. I tried changing the spark plug and it still won't start.