Strange idle

[Tom14]

Hi all I've just bought a second hand hyper 7 mac 28 it idles fine for about 15 mins of driving then it starts to idle like his and can't get ithe to change unless it cools right down. I've tried too upload a video but it won't let me. All I can say is that it sounds like a popping noise

 

[olds97_lss]

Put it on youtube, then share the link.

 

[Tom14]

 

[olds97_lss]

Could be an air leak around the carb neck or front bearing. Once it warms up, things expand a bit which is when a leak can show up. Or it's tuned a bit lean and doesn't get fully heat saturated for a tank or so, so it seems fine until it's fully up to running temp and is too hot.

 

[Tom14]

The running to lean makes sense cause when I stopped the car I could hardly touch the engine, I'll try richening it tomorrow if that doesn't work ill strip it and seal it, if that doesn't work I'm buying a new engine lol, thanks for your help

 

[olds97_lss]

Do you have a temp gun? If not, get one. Especially before you pony up for a new engine. Decent running temp for most nitro engines is 210F-260F. Much more or less isn't great for them.

 

[Tom14]

I bought a temp gun and it was reading 240 but still popping and not running right so I've put it in the shop to be fixed thanks for all help

 

[olds97_lss]

Strip it, clean it, seal it. Does it have a composite/aluminum insert carb or all composite or all aluminum?

Sealing an engine:
https://www.rcnitrotalk.com/forum/threads/nitro-tuning-tips-and-tuning-flow-chart.60832/#post-726317

 

[Tom14]

Strip it, clean it, seal it. Does it have a composite/aluminum insert carb or all composite or all aluminum?

Sealing an engine:
https://www.rcnitrotalk.com/forum/threads/nitro-tuning-tips-and-tuning-flow-chart.60832/#post-726317

I couldn't tell you without looking at it mate, its already in the shop for a standard tune up to see if that solves it, if that doesn't work i think I'll have to strip it down cause someone else said it could be a gasket gone. I'm only new to the rc scene so didn't want to mess the car up before I've properly had a play lol

 

[olds97_lss]

Ah, wasn't sure if you were new to nitro or not. Some of the composite/alloy hybrid carbs have leaking issues as well and don't present much of an issue until they are warmed up. They use composite to keep heat saturation out of the carb so the fuel doesn't boil causing vapor lock (I think that's why). Over time and with abuse, the bond between the composite and aluminum can break down, which lets air in as things expand when the engine warms up.

 

[Tom14]

Ah, wasn't sure if you were new to nitro or not. Some of the composite/alloy hybrid carbs have leaking issues as well and don't present much of an issue until they are warmed up. They use composite to keep heat saturation out of the carb so the fuel doesn't boil causing vapor lock (I think that's why). Over time and with abuse, the bond between the composite and aluminum can break down, which lets air in as things expand when the engine warms up.

If it helps it's a standard mac 28 6 port engine with a turbo head apparently lol. By the look of the car it has hardly any use at all, no stratches on bottom and most of the screws were loose, like it had come straight out of the box. If it hasn't been ran in properly could that cause it or damage the engine?

 

[olds97_lss]

Wouldn't do it any favors. But if it's not finished break-in, that could also make it run weird. Most engines I've had are pretty fussy for the first 1/2-3/4 gallon. By the time you get 3/4 gallon through them, the tune gets pretty solid... unless it's a traxxas engine. Those befuddle me every time.