high rpm crackle

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Rcnut24

Rcnut24

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looking for help. My son is tuning his 30.5 cy and at high rpm it crackles and or breaks up. he has changed plugs and tuned. runs good for a bit then acts up. any ideas??
 
Seandonato73 said:
Not without hearing it, but I'd suspect he's too lean. Or out of gear, but lean would be my first thought.
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we my son and I have different opinions on what is causing it. for the first few laps around our yard it runs good. then the crackle slowly moves in. It also acts up on the stand free wheel no laod.
 
Hard to tell not being there. How hot is the engine getting? Primer bulb still full? Did he swap out the carb isolator for a bullet version? Got any videos of it doing it you can post?
Not making fun or anything, but your saying my car don't run right, how do I fix it.
 
has the stock carb spacer not billet. primer bulb half full. not sure how hot its getting. and you are correct. I'm not a 2 stroke engine guy. I have built many race engine for go carts, stock cars and a quad. so yes looking for help.... 16647377673623289114296810051431.webp
 
Let's start off by its a clone engine with subpar base metals, and like sean said it can literally be anything without looking at it. We see people here with more running issues on cy clone engines than we do with zenoah or big bores. Yea we all suffer time to time with anomalies but in your case the elephant in the room is the cy engine. Your going to have to tear the engine down if you don't see anything obvious, take the carb insulator off and check it with a known flat surface to see if it warped as those always warp at some point.
 
Rcnut24 said:
has the stock carb spacer not billet. primer bulb half full. not sure how hot its getting. and you are correct. I'm not a 2 stroke engine guy. I have built many race engine for go carts, stock cars and a quad. so yes looking for help.... View attachment 83753
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Looks lean to me.
If it only happens when it gets hot it's probably the carby.
I'd replace it with a Walbro 668 on that size engine.
It may save you a tear down and rebuild.
 
That plug has had like three tanks through it. As for the carb it's a stock redcat rampage chimera 30cc buggy.
we are new to the gas rc without much homework first. there isn't much info in the manuals I think it is a 668 on it.
 
i can tell you a bit about clone engines and carbs.... the carb that came on my 30N was branded walbro but ran like shite and wouldnt idle or run right. tune it and get it running well, stop the engine and start it straight away and it would be rich or lean. i say replace carb with a guaranteed genuine one from rcmodelz or taylor rc (UK) or ddm racing in the US. now the engines on the other hand arent too bad for a year or so but you'll start to notice the quality problems later on so swapping the engine out to a zenoah once you can afford it will always be worthwhile.
Phill2 said:
My Redcats had clone 668s on them.
Take it off and check that it has Walbro on it.
If not replace it.
Also check all engine bolts are tight.
One of mine came out of the box with loose head bolts.
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replace it end of, i had a supposed genuine walbro on my 30N... ran like shite, put a proper walbro on there and was perfect and has been for 8 litres now. original carb i spent about 2 litres of fuel faffing around
 
Ollie said:
i can tell you a bit about clone engines and carbs.... the carb that came on my 30N was branded walbro but ran like shite and wouldnt idle or run right. tune it and get it running well, stop the engine and start it straight away and it would be rich or lean. i say replace carb with a guaranteed genuine one from rcmodelz or taylor rc (UK) or ddm racing in the US. now the engines on the other hand arent too bad for a year or so but you'll start to notice the quality problems later on so swapping the engine out to a zenoah once you can afford it will always be worthwhile.

replace it end of, i had a supposed genuine walbro on my 30N... ran like shite, put a proper walbro on there and was perfect and has been for 8 litres now. original carb i spent about 2 litres of fuel faffing around
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The engine is a fulie on a red cat chimera. Purchased prior to research and have since been buying rovan. so as we have issues we are slowly switching things over....we swapped the engine and ended up with the same issue.....In turned out to be starving for fuel. once it starts loosen the cap and runs fine.
 
Rcnut24 said:
The engine is a fulie on a red cat chimera. Purchased prior to research and have since been buying rovan. so as we have issues we are slowly switching things over....we swapped the engine and ended up with the same issue.....In turned out to be starving for fuel. once it starts loosen the cap and runs fine.
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rovan really is no better than fuelie. ah yeah blocked fuel vent, on the underside on the fuel cap there will be a rubber bulb, pull that out then there will be a plastic fuel stop that stops the fuel flowing out if flipped, just check if its blocked anywhere
 
Ollie said:
rovan really is no better than fuelie. ah yeah blocked fuel vent, on the underside on the fuel cap there will be a rubber bulb, pull that out then there will be a plastic fuel stop that stops the fuel flowing out if flipped, just check if its blocked anywhere
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we are still learning as we go. have found some nice places to purchase good parts. I have build many race engine for stock cars and i am going to be building our engines in the future soon. I have access to a machine shop so just picking up some tips here and there.
 
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