2-Stroke 300cc Top End Rebuild!

Spencer and Cole work on Cole's bike to give us a backyard, maybe more realistic average guy top end change. If you shop online at Rocky Mountain ATV/MC please click this affiliate link to shop in the future. There is no extra cost & it helps support our channel. Remember to click this link RM ATV/MC -DBTV Shopping each time you need to go there to shop. www.rockymountainatvmc.com/l/...
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Jay Clark/Dirt Bike TV has been around the Dirt Bike industry for thirty years and is always looking to learn and help others do so as well. Give a follow or drop an email if you have any questions or comments. Thanks for watching!
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#dirtbike #300xc #KTM

[@TheCarlejoseph]

Great video. Thanks for the tips.

[@spencerclark2269]

Fun video. Realistic job

[@kimojon9665]

Just want to add to those out there wanting to do this type of work, correctly. Go to Tokyo Offroad videos to get the right information. In this video, there was no deglazing of the cylinder, when tightening the cylinder, at least tighten in a cross pattern, not one side and then the other. Also, do not put silicone on the power valve rubber seal and use a torque wrench on all bolts you can access. Last, the information of the day provided by the chubby Einstein guy, "if there seems to be something catastrophically wrong with the bike, just stop riding it" duh...

[@dirtbiketv1]

I couldn't agree more --

[@barkeep25]

You must be really popular at parties.....

[@bloomerb4162]

Why is it a bad idea to put sealant on the PV rubber seal? I put yamabond on mine.

[@Fmontes]

Can't believe how young Jay looks in this video.

[@westcoastfrisco]

💀

[@cooliomilkman]

My thoughts exactly

[@rene5853]

Putting a new piston makes you look younger like brand new

[@moorefab8192]

Anyone know if you can use a 2004 and newer piston for a 300exc in a 1999? And if not, why not, what’s different? The newer piston kits are half the price than I’m seeing for the 99-03

[@bloomerb4162]

Why would you put a c size piston in it, if it had 180 psi of compression with the 100 hrs piston?

[@dirtbiketv1]

Email Jay directly with any questions. Contact info in About tab.

[@elkku2934]

Do you know if Pro X pistons are any good?

[@Bubbleuprubberdown]

You can anneal copper washers and get two or three uses out of them.

[@jjjjjjjjrifufjssjosskenf]

Or just buy new ones, they are cheap

[@chrislalonde8180]

You guys didn't deglaze the cylinder??

[@estebans6472]

2 strokiiessss

[@thewangster123]

Hey guys, what premix ratio is Cole running in the 300? Cheers

[@colechristensen25]

Amsoil Saber 80:1

[@HuntertheHoleshotKing]

What 2 stroke oil did he run for those 100 hours and what ratio?

[@colechristensen25]

Amsoil Saber 80:1

[@rdgsupafli]

Is it normal to have that wear inside the cylinder bore?

[@dirtbiketv1]

You can email Jay directly with any questions - contact info in About tab.

[@wilderenduro7096]

Wouldnt it be better to go by compression instead of every 100 hours?

[@colechristensen25]

Compression test was 180psi before. 185psi after. Very little change. We don’t wait till there’s a drop in compression. Just hourly intervals.

[@bloomerb4162]

Wow that's incredible with 100 hrs.

[@robertococcia9815]

With your old piston another 50 hours of use

[@davidalexandru9176]

How do i choose the piston corect size?

[@dirtbiketv1]

People can set sag how they want but anyone worried about a 2/3mm hole in the fender has their priorities mixed up.

[@ducaduke]

Those 300s go for 300+ hrs hard riding on the stock Piston

[@shannonscott5788]

Only if it could really be done in 23 minutes….every year, every year until you either get tired of doing it or can’t afford a top end plus labor…..🤔😬

[@jesserichter7560]

I won't buy another vertex piston one I bought wrist pin wouldn't fit thru bad machine work

[@jakewood4329]

Can't believe u guys are doing a video on how to do new top end piston change an don't have torch wrench !???....🤬🙃😴

[@colechristensen25]

Forgive us

[@chadrides914]

Torch wrench? What did you expect them to have to heat up the bolts or cut metal?

[@jakewood4329]

Haha all good I was just surprised u guys did without one

[@fishtailfuture]

Every video I see like this with guys going 80 hours. 100 hours I just like to point out that as this gentleman said. Next piston he's gonna have to re-plate. And I know guys that will put 100 or 120 hours on a piston and replaced their cylinder every two or three pistons. And if you're like me and ride 4050 or even 60 hours in one season. Change of piston. Even if we only did 40 hours. Because 80 is too much and if you go longer the next year and you don't replace it, you're hitting that 100 mark. You will be replacing your cylinder as well. What you can get out of a motor is not what you should do even if you're a woods rider. You start to see blowby and the scuffing in this video at around 60 hours. Almost every single piston. If you are a slow trailes rider, I would replace it before then. A piston that is changed often the cylinder can last seven or even eight pistons. Which is about 340 hours versus 240 hours if you run it 120 hours each time.

[@SpeedDemonExpress]

Not smart putting in a C piston without measuring the piston to bore clearance.