DHM High Compression Stock Bore Piston for Honda Grom/Monkey | FULL INSTALL AND TIPS!

MORE POWAH BABY! There's a lot to know about this one, and - I. COVER. EVERYTHING in this video!
Sorry about running mid-roll ad's on this. I know they're a pain, but this video was a monster to create and edit (surely as you can tell from it being 30+ minutes long). Hopefully it serves as an instruction manual for you and you understand my choice to monetize it based on the effort it took me. Thanks!!
What we have is a very special product from DH Motoring. This is a stock bore sized, high-compression (13:1) piston for the Honda Grom/Monkey 125. Stock bore is desirable because it won't heat up like a big bore, and won't require an oil cooler. It's also desirable because you can use your stock cylinder, which makes it super affordable. High-compression is desirable because it makes POWER!
I won't go into detail on the kit as I did that in my What's on the Bench? video about it here:
• What's on the Bench? E...
This install video covers everything except the removal of your stock airbox because I don't have that on my bike, and didn't need to remove my MNNTHBX Mtake to do this job. I also didn't highlight the factory manual procedure because I felt it was requiring you to remove too much, and found my own shortcuts around having to remove the throttle body, which would've been a pain. You might notice in the video that I don't show myself placing the ring gaps 120 degrees apart because the camera angle was a bit bad or difficult to show. Just remember to ensure the gaps are not lined up with each other, and a good rule of thumb is to space all 4 gaps out evenly and I really don't think it matters where on the piston they are, but I show the diagram from the manual anyways.
Here's some important links for the products I used:
DHM High Compression Stock Bore Piston (Gen 2) (add spark plug): www.dhmotoring...
Proform 66785 Piston Ring Filer: amzn.to/34HAdVo
Feeler Gauge: amzn.to/3nYn9mt
Honda Monkey Official Service Manual:
www.helminc.co...
Gear used to film and produce this video:
Camera - Canon M50: amzn.to/37Jz4hY
Mic - Rode VideoMicro: amzn.to/2KmBuun
Joby Gorillapod Handheld Tripod - amzn.to/3pgsHZF
AmazonBasics 60-Inch Lightweight Tripod with Bag: amzn.to/34GbyAK
Apple Macbook Pro: amzn.to/38wMTQ7
Editing Software: Final Cut Pro X
Hat: amzn.to/3ay8BWG
Shirt: www.yoshimura-...

[@sidneytorresjr7284]

I know a little bit about cars/bike/engine/etc, but am learning more and more each day. You are the first person I've come across that explained the importance of the ring gap that made sense to me. I'm sure plenty of others have and I just haven't seen those videos, but thanks for that. Subbed.

[@John5XR]

I appreciate your feedback on this, I love the technical details and I’m certain cases like this, feel they’re important

[@landonfolken03]

I was looking at getting one and decided to look up installs and hey you've got one for this as well!! Outstanding!

[@keithgordon702]

Excellent step-by-step graphics accompanying the video. Well done :)

[@1983thunderbird]

Great job with the video and install. Your videos are very thorough!

[@John5XR]

Thanks!! This one was ultra-thorough and I felt it needed to be due to the meticulous nature of the install. Didn’t want any important info left out, and I spent a good deal of time making sure all of the info was pertinent and not rambling. That’s hard for me to not do! Lol

[@cairoabel2068]

InstaBlaster...

[@monkey_powered_alex3231]

Very good and educational Video. Keep up the good Work💪 Picked up my Monkey last week 😁 Greetings from Germany

[@John5XR]

Thanks Alex! Enjoy the bike

[@thomasanderson1159]

Keep it up brother.. You've inspired me to learn all about the ECU mapping and different tuning options for the monkey and motorcycles in general. Kudos!

[@thomasanderson1159]

Just wanted to add that I tried to buy you some coffee and it say's the Card number is invalid. Its a good standing visa, just a heads up if you are not receiving support it may not be working properly.

[@John5XR]

Love hearing this Thomas! Glad I was able to bring the wonderful world of motorcycles and the ever complex madness of ECU’s to you! I appreciate the support too, the effort means a lot, even if that card didn’t go through 🙏

[@thomasanderson1159]

@@John5XR Got you 3 coffee this morning! Support site is working just fine, Stay cool!

[@John5XR]

I appreciate the hell out of this brother! Any earnings (mostly from my savings though, lol) from my channel go straight back into the bikes 🙏

[@AugustinesHeart]

I’m just about to do this mod. So glad you’re reviewing it, and that it’s going to add the power. I’m taking it in to have it done though, I don’t trust myself with the rings.

[@John5XR]

I think it’s a great mod, but I also think I flubbed up the ring like I thought and lost potential power from it. The gap is important and too much will be safe, but you’ll lose a bit of compression if it is, and a lack of power

[@AugustinesHeart]

I saw this video is like 5 months old, my Monkeys been neglected through winter, but did you end up fixing the ring? Even with the bigger gap, did you notice more power? I’m looking to get their titanium axles now too. I’m going to do the piston in August and hopefully with that, the lithium batter, gearing, intake, exhaust, and cam, I can get it as fast and torchy as I can get it to go without the big bore. Did you ever do a Speedo healer?

[@John5XR]

I don’t feel as if I got any more top speed, but it sure does feel more punchy, like if you wanna do a wheelie, it’s gonna do a wheelie! Never did get that speedo healer though... 😂🤷🏼‍♂️

[@cookjc1]

Nicely done once again.... Keep em coming!

[@John5XR]

Thank you, and will do!

[@robertyoung8289]

Very educational. Thanks John!

[@John5XR]

Thanks for watching and commenting Robert!

[@michaelzuccaro1798]

Great job again. You've done so much.i did the 14 and 37 tooth sprocket changes.ill have to hunt down someone who lives close by me in California or lake havasu Arizona with your mods so I can compare.report on what you think of the new piston.thanks mike z.

[@John5XR]

Thanks Mike! It’s been fun conservatively modding the bike, but I did see a need for a bit more grunt when I hit the hills and mud on the trails on my NY trip. I’m thinking this piston will provide that extra pull. The 14/37 is a great choice!

[@trialsk1d871]

Its a good kit I have over 4k miles and not 1 problem.

[@John5XR]

Good to hear! I won’t hit that kinda mileage, but I like to hear it has longevity

[@wadehoagland9188]

looking forward to hear your review if its worth it. thanks

[@John5XR]

Me too! Hopefully I’ll get some riding time in soon, life’s been a bit packed since I installed it this past weekend

[@speedmonkeyadams8985]

Which ring goes in which mark?

[@terrylmonterastelli3395]

I think just a small amount of port work would’ve done really good along with the addition of that piston

[@auomauom]

Thanks for the step by step tutorial! Im going to be attempting this once I get the kit. I have a question about TDC. Once I set it to TDC, remove the head and jug, will the TDC markings move?

[@John5XR]

Thanks for watching and commenting! It’s not the most important thing to keep in place, you’ll have to recheck the marks when putting the chain on anyways. It’s just good practice to try and keep it there to make sure it goes back together the same way. The cam doesn’t move, so that makes it easier.

[@LattManthier]

Can you check if the spark plug will actually hit the piston with out that spacer? If it doesn't actually hit your losing compression

[@Ferchap1820]

Great video I enjoy them. Quick question never done motor work I just ordered this piston ecu and canm. I see that the piston rings top and bottom go 120 degrees. But the two bottom ones that hold the oil rings that go in the bottom you align them together straight at 120 degrees or they go 120 a part so it would look like a square type scenario. Thanks for the help.

[@John5XR]

I actually missed that when I shot the video so I put the snip of the manual in there for the ring orientation. You would space all of the ring gaps at 120 degrees, but an easier way to think about it is the top ring gap at 2 o’clock, the 2nd ring gap at 10 o’clock, the top oil ring gap at 5 o’clock, and the bottom oil ring gap at 7 o’clock. The oil scraper ring will interconnect.

[@Ferchap1820]

Ok thank you so much🙏🏻 great videos. Keep em coming. 👍🏻

[@beardedthunder8363]

Great video! Stupid noob question. I have to gap the top two rings not the two oil rings? Never done a piston before.

[@John5XR]

Correct, the oil rings do not need to be gapped

[@joecamel6835]

@@John5XR It's too much power !

[@reeupp1257]

So I just installed the high comp piston but forgot to oil up the cylinder walls and piston (rings & wrist pin). 🤦‍♂️ I started it for the first time with fresh new oil and let idle for 5 min. Then I test rode it for about 20 miles with no issues. Do you think I’ll be fine or do you think i should tear it apart again?

[@Ferchap1820]

I got this same piston to be installed what’s the gap for the spark plug? And have you had any problems with it. I’ll be installing mine over the weekend. Great videos brother. Keep em coming.

[@John5XR]

Ya know, I’m not sure! I didn’t adjust the gap, just went with it out of the box. No problems after about 25-miles of riding, both low speed and wide open throttle for long periods of time, so all seems well. Enjoy!!

[@Ferchap1820]

@@John5XR ok thanks I’ll install like that. Great videos brother

[@oim125garage]

Awesome🎉

[@taylorgray6223]

When you ordered the Piston from dhm did they send you new gaskets too or did you have to buy them separately? & also did it come with the wrist pin clips?

[@diysewinglessons2423]

great channel . Can you do a review for the corbin Solo Saddle for 2019-2020 Honda Monkey ?

[@diysewinglessons2423]

the corbin looks like it`s good for two person but there is no youtube video about it

[@John5XR]

Thanks! I’ll have a look at the seat and see if it’s something that I can use for my bike. I take my kids for rides on the bike often, so it might be of interest to me.

[@ericcooper2174]

That oil ring will be fine

[@John5XR]

So far so good! Lol

[@MegaBunnySlayer]

Hey. What's the valve clearance for the stage 3?

[@carenthusiasts7253]

.003

[@MegaBunnySlayer]

Thank you 😊

[@AndrewDasilvaPLT]

Did you notice an increase in power AND/OR increase in oil temp afterwards?

[@John5XR]

yes for sure. The gains are mostly in the low-mid RPM range, but they're helpful for getting up and going faster. Couldn't say on oil temps, as I have no real way to measure them accurately. DHM confirmed that an oil cooler is not necessary with the high compression piston though.

[@chuckbowen4334]

Usually higher compression will make it eyn alot hotter. Not goid on a aircooled bike. Even adding a oil cooler wont help alot. You need to increase the cooling fin size. We used to do it on the xrs we used to race.

[@John5XR]

Agreed.

[@hannesdobbelaere]

why did it require you to put a spacer on the spark plug, you're taking away some of the compression you just made by installing HC piston? is the piston that much higher that it would touch the spark plug at TDC?

[@tonnitropartas]

Yes, without the spacer, the piston will smash the spark plug

[@JesseeS1990]

I noticed you installed brown side of the gasket up. I just received mine with the only way to install is with brown side up as well, yet other videos and any other gasket I’ve installed has been green side up. Was this a production issue or by design?

[@John5XR]

Great question and I wish I knew! I’d have to watch the video again, but it might only go one way due to the bolt pattern leaving only one choice

[@estufados]

Hello John, it 's necessary to install a new ecu? Or only with the high compression piston and the stock ecu will work? Where I live they don t sell the Dhm piston only the kitaco one and it comes without the ecu modified... and another question, I've just installed a tyga exhaust but it feels that I don t use 100% of the exhaust, what can upgrade without puting in risk the engine? Thanks John!

[@John5XR]

While you can add the mods without an ECU tune, it's not going to provide any gains because you're going to starve it for fuel and the air/fuel ratio will be lean, which can be detrimental to the engine long-term. Exhaust only, intake only, or piston only would help, but all together would need an ECU reflash

[@Shmack_]

Waste of money without tune

[@wweyrauc]

Are you going to do any head work? I think you have a flashed ECU on the monkey, are you doing another flash?

[@John5XR]

Haha, well with the way this bike is going, that might be a possibility! I didn’t wanna get too deep into engine mods with the Monkey, but if I keep getting the manufacturers wanting me to do install videos, probably 😁

[@John5XR]

And yes, the ecu is now flashed for my intake, exhaust, cam, and high-comp piston

[@wweyrauc]

Nice, look forward to seeing your review of the piston. Looking at a similar setup, but thinking about adding a ported head to maximize everything.

[@John5XR]

I’ve put a few miles on it around our backyard tracks and around the neighborhood and it feels more powerful already. I’m yet to do a top speed run as I want to let those rings seat in a bit

[@wweyrauc]

@@John5XR yeah, do a proper break in then let everyone know your thoughts.

[@natekelly35]

Hey John, give up an update on your results when you have a chance! I just did a DHM piston install this week myself and felt I may have slightly over filed one of the ring gaps slightly. Here's hoping it holds up as well as yours.

[@John5XR]

Will do. Do you think it affected performance?

[@natekelly35]

@@John5XR It has, but maybe not in the way you might expect. There is a different engine note and the main takeaway I have found 100 miles into the break-in is that I'm gaining about 3-4 MPH between shifts, but the power gained is very subtle. Still, a great upgrade and opportunity to install the Gromfatherz HD Studs and Head Bolts.

[@John5XR]

Cool, I’ll be monitoring it for sure and updating as I think it’s something that happens very easily

[@natekelly35]

@@John5XR One more thing - I spoke with David at DHM and it sounds like that ECU you got with it will really help out in avoiding the issues I'm having.

[@John5XR]

@natekelly35 the ecu will absolutely help with providing the extra fuel and timing needed to allow the piston to be most efficient at making power. Along with the Yoshimura exhaust, MNNTHBX Mtake, and TB cam, the extra airflow will definitely need more fuel. Having the ecu reflashed to your specific mods is certainly a “must” as you never want to run with a lean air/fuel ratio (not enough fuel) on an air cooled bike, as the fuel provides a fair amount of the cooling for the piston

[@AndrewDasilvaPLT]

Have you noticed a significant amount of increase in power?

[@John5XR]

significant, no. noticeable, yes

[@TheImtoomuch]

Good video. Very thorough. Shame on DHM for not labeling the piston rings or at least specifying location by color on the instructions. I wonder how accurate those cheap feeler gauges are. Also, because you live in Florida I wonder if would be safer to go to the top of the ring gap tolerance to allow an extra .001” for the extra heat you guys have down there. Just thinking out loud. I’m guessing being in the middle is perfectly safe. I like that you leave in your mistakes, such as making the lower ring gap too large. We all make errors. And we all can really learn from mistakes. No reason to hide it.

[@John5XR]

All great points, thanks for commenting! It would have been nice to know for sure on the rings, however I didn’t reach out to DHM to ask, which I’m sure they would have told me. On the feeler gauges, yeah, I should measure it with my Amazon digital caliper to be sure! 😂🤦🏼‍♂️ Bigger ring gaps might be better down here and I’d want to err on the too big side on an air cooled bike since it runs hot. The downside would be a loss of potential compression, and maybe some oil blow-by. I’m not worried about losing a little peak power potential as I’m not racing, and if it blows by a little oil, I can see how bad it is and make a decision based on how much. Yes! I left the mistake in because it’s sooooo easy to make and think people will be more aware of the process and attention needed to do it right

[@xsheashea]

How is this holding up? Would you recommend?

[@John5XR]

Holding up great! I think a bigger ring gap is safer (which was a mistake) but you won’t get as much power with a big ring gap. Try to nail that gap size

[@seanwhitelock2791]

why didnt you clean the old gasket off

[@123sysysy]

25:50 you need to change the spark plug

[@John5XR]

Good tip. It doesn’t seem to be an issue when it warms up, but maybe the plug gap could use re-gapped

[@123sysysy]

​@@John5XR You need "cold plug" or more heat range spark plug because you had high compression ratio

[@John5XR]

Interesting. I’ll bounce this off DHM to see what they recommend

[@YT_Jonathan_GT]

Good video man, I’m currently installing one on my Grom do all the rings need to be gapped or only the very top and bottom under it

[@M074503]

that yoshi monkey shirt is cool! they are out of stock and i cant find my size :[

[@horne300]

Did your mpg decrease after all these mods?

[@wileecoyote5749]

Obviously

[@EstebanAGaido]

What happened to your Yoshimura RS-3 exhaust? :|

[@John5XR]

It’s back on now, was waiting for the DHM piston to be installed to go back to braapville 😬

[@Shmack_]

No oil cooler needed?

[@John5XR]

Not for this, but for a big bore kit yes

[@Astigmotofi]

What size piston ????

[@John5XR]

Stock size, but higher compression

[@chuckbowen4334]

Yes.. it adds power but, at great cost

[@John5XR]

What’s the cost?

[@logantolley4192]

when you do an high compression piston your supposed to check your piston to valve clearance! Because the top of your piston when putting in an high comp piston or an high lift cam can hit your valves or just barley tap them and make a knocking sound in your engine. .

[@John5XR]

I would if this wasn't already engineered by a Honda Grom/Monkey performance shop. Where I really messed up was making the ring gap too big and not honing the cylinder first...

[@auomauom]

Those 5 uggs on the cam shaft bolt cringe...

[@John5XR]

the impact is a 3/8" light duty, doesn't provide a load of torque like the big boys. Unless you have a pulley holding tool, this is a good way to get that bolt tight. But yes, it's not the "ideal" method, but the realistic method for most of us

[@auomauom]

@@John5XR btw DHM just emailed me back about the compression rings. He said black ring is top, sliver is bottom.

[@John5XR]

If that’s the case, I got it wrong... Thanks for sharing that 👍

[@auomauom]

@@John5XR how many miles have you put on the piston? No problems yet?

[@John5XR]

Probably 50-75 miles so far. No issues at all!

[@reidspeed77]

Didn't sound healthy

[@wileecoyote5749]

Stock sounds same