Custom 70cc engine build

Is it worth it or stupid?

  • YES

    Votes: 19 63.3%
  • Hell no

    Votes: 2 6.7%
  • Kinda

    Votes: 4 13.3%
  • YES

    Votes: 3 10.0%
  • Nah I'll pass

    Votes: 2 6.7%

  • Total voters
    30

Z.hb71

Well-Known Member
Messages
5,614
Location
Hoffman Estates, Illinois
Also can I just let you guys in on something. You know I would talk about a winter rebuild of my truck? I don't think I'll do exactly that, sure I will do a small rebuild as in, replace bearings and do a screw kit, that's it, I won't do any upgrades except for maybe tranny gears and just save my money. Let me explain, for one I won't have enough money for all the stuff I wanted to do as the build took way too long and way to much money, and second, id like this truck to be bare minimum, fek load of power but just enough upgrades for it to be reliable for 2 reasons, it's cheaper but the main reason is, I'd like to still have room to upgrade and change stuff up, if I upgrade it all at one time I won't have anything to break and fix really. So I'd like it to be bare minimum and keep upgrading as I go along, like the good ol days of the rovan 30cc (you guys don't know that world as I wasn't here @ that time) πŸ‘ and I'd like my next RC to be all out, no expenses spared type of thing. Whenever that time comes.
 

AnubisBC

Well-Known Member
Messages
170
Location
Portland, Oregon
If you must temp check, get a really good IR thermometer if you don''t have one already. The best one I've ever used is a Nebo Tempra (https://www.amazon.com/Tempra-thermometer-EdisonBright-batteries-bundle/dp/B01JRHJDP4). It's truly amazing! It has 3 emissivity modes so you can get an accurate reading on any surface, a laser and a built in flashlight. It's stable, accurate as hell and worth more than double the $50 price tag. You would typically want to take a reading as close to the spark plug as you can, and as soon after stopping as possible. Otherwise the case will load up and start cooling your motor very quickly. Some people opt to measure the crank case temp instead, but that won't give an accurate head temp, which is where all the magic happens.

But in all honesty, you shouldn't need to check your temps on a motor that size. Just listen to the sound and keep an eye on the plug color after break in. You never see 2 stroke motocross guys tuning on temp. It's all about feel. If you're running too lean, the engine will sound kind of dry, like it's winding out, and will struggle to hit the top of its RPM range. If it's too rich, it will make a burbling sound and struggle to hit the top of the RPM range. If your motor tops out without sounding like it's struggling, you're good to go!

As for upgrades, you know me man. I'm all about running what you have until you break shit. Once it's broken, then I'll upgrade. I'm still running the stock 4mm shocks for hell's sake! And I've taken my truck through some seriously stupid beatings and a lot of big air. I'll tear her down between big runs to make sure the bearings are all good, and the shocks are topped up. So far, I've only had to upgrade the A-arms, drive shafts and drive boots due to breaking stuff. All my other upgrades are pure performance and quality of life stuff.

I'll eventually kill the poor drive cups and need to replace the drive pins. And I'm honestly hoping my engine upgrade gives me an excuse to get some more bits, but if she holds up, I won't bother.

But hey, in the end, this hobby is about the pure joy of running and wrenching these bad boys. Do what makes you happy, and share your results!

TLDR: Don't need temp gun; just fekkin' enjoy yourself! We won't judge!
 

Z.hb71

Well-Known Member
Messages
5,614
Location
Hoffman Estates, Illinois
If you must temp check, get a really good IR thermometer if you don''t have one already. The best one I've ever used is a Nebo Tempra (https://www.amazon.com/Tempra-thermometer-EdisonBright-batteries-bundle/dp/B01JRHJDP4). It's truly amazing! It has 3 emissivity modes so you can get an accurate reading on any surface, a laser and a built in flashlight. It's stable, accurate as hell and worth more than double the $50 price tag. You would typically want to take a reading as close to the spark plug as you can, and as soon after stopping as possible. Otherwise the case will load up and start cooling your motor very quickly. Some people opt to measure the crank case temp instead, but that won't give an accurate head temp, which is where all the magic happens.

But in all honesty, you shouldn't need to check your temps on a motor that size. Just listen to the sound and keep an eye on the plug color after break in. You never see 2 stroke motocross guys tuning on temp. It's all about feel. If you're running too lean, the engine will sound kind of dry, like it's winding out, and will struggle to hit the top of its RPM range. If it's too rich, it will make a burbling sound and struggle to hit the top of the RPM range. If your motor tops out without sounding like it's struggling, you're good to go!

As for upgrades, you know me man. I'm all about running what you have until you break shit. Once it's broken, then I'll upgrade. I'm still running the stock 4mm shocks for hell's sake! And I've taken my truck through some seriously stupid beatings and a lot of big air. I'll tear her down between big runs to make sure the bearings are all good, and the shocks are topped up. So far, I've only had to upgrade the A-arms, drive shafts and drive boots due to breaking stuff. All my other upgrades are pure performance and quality of life stuff.

I'll eventually kill the poor drive cups and need to replace the drive pins. And I'm honestly hoping my engine upgrade gives me an excuse to get some more bits, but if she holds up, I won't bother.

But hey, in the end, this hobby is about the pure joy of running and wrenching these bad boys. Do what makes you happy, and share your results!

TLDR: Don't need temp gun; just fekkin' enjoy yourself! We won't judge!
I'm not gunna tune by temp or anything like that, I'm checking just to make sure it doesn't overheat when idling for 15 mins.
 

AnubisBC

Well-Known Member
Messages
170
Location
Portland, Oregon
I'm checking just to make sure it doesn't overheat when idling
Derp! My bad, didn't even think you would just be idling. Nevermind me!

The duratrax should be sufficient for your needs if you can get a clean reading next to the spark plug. You're just trying to avoid under/overheating. It's not like you're doing anything that requires extreme temp accuracy, like candy making.
 

Z.hb71

Well-Known Member
Messages
5,614
Location
Hoffman Estates, Illinois
This is as far as I got for now.
i shouldn't have stopped gassing it because it probably would have kept going if I let it warm up a bit. But that's what it sounds like. Also I think I probably should have gone for a lower squish, I'm running about 1mm squish and Athena suggests .7mm. so it's a bit off and I could probably gain a bit of power and compression with it. The only reason why I did this is, my shitty calipers only do 1 mm increments and I didn't want to just eye it, it still makes a lot of compression just not as much as it probably should be. So I'll deal with that when I get a proper calipers, which is next on the list. Oh and I'll keep trying in a hour becuase my drill started to shit itself and overheat (go figure). I'll keep y'all posted.
 
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