[Jamesstone]

Afternoon all,

Signed up to the forum for inspiration & support to get this project finished in the coming months (that's the plan anyway)

I run a small YouTube channel following my love for cars/bikes and have always been more of a "bolt on" builder than custom fabrication and have always wanted to try my hand at an engine swap - what better base than a Grom!

I've done the normal pass your test, keep going through the ranks of getting faster and faster bikes over the years combined with track days & last year a trip to the Nurburgring on my KTM RC8R but there is something cool about the Grom that builds my desire to put a bigger motor in one.

First episode filmed before Christmas (just waffling more than anything)

Collected the bike last month, nice low mileage 2017 model, under estimated its size for a small bike but thankfully still managed to squeeze it in the back of my friends Kia without causing any damage to the car or bike.

The following day it was time for the deep clean, really tidy little bike (probably to good for stripping/hacking to bits to be honest) but the previous owner had been using it through winter back roads without washing so combined with the dark evening it was a bit of blind purchase.

I completed a temporary fix on the split exhaust to complete the stock road review video, it almost held up but fell apart on the last leg of the journey as detailed in the video. Very loud and embarrassing

The first ride out video on the stock engine, actually really good fun and nippy enough unto 30mph! being 93kg/6'2 tall I managed a best top speed of 60mph lol...

I'm a massive Ken Block fan for the company/brand he built whilst still enjoying the sport professionally, as I'm sure most of you are aware he's passing last month was sad news! I've always enjoyed he's bonkers powered cars so what better name for the project than the HOONIGROM (the plan is to complete the build in the original Hoonicorn colour scheme too)

Next video will be stripping it down and selling off all the stock parts I won't need, originally the idea was to fit a 250cc single but my friend advised 300cc as it wasn't going to be a great deal larger and would be even more bonkers, the biggest issue I can see is getting suitable size radiators in place to keep it running at the correct temperature but this will all be part of the fun!

Comments welcome

 

[mingo]

Thanks for sharing your build.. very interested in how you'll do this!

 

[Jamesstone]

The engines out, no going back now!

Wasn't a big job to drop the motor thankfully, pretty straight forward!

Disappointing to see how much paint is flaking and surface rust on the frame for a 2017 model that's only covered 3,700 miles. Its clear Honda's mighty build quality isn't the same as 20 years ago.. I go into more detail on this in Sunday's video, plenty of clips on dropping the engine so hopefully that alone will help a few out

Thanks for sharing your build.. very interested in how you'll do this!

Provisionally secured a Gasgas EC300 which should be collected Friday, then I can have my first real look/head scratch at how to make it work, certainly not going to be a 2 minute job lol..

 

[shush319]

The engines out, no going back now!

Wasn't a big job to drop the motor thankfully, pretty straight forward!

Disappointing to see how much paint is flaking and surface rust on the frame for a 2017 model that's only covered 3,700 miles. Its clear Honda's mighty build quality isn't the same as 20 years ago.. I go into more detail on this in Sunday's video, plenty of clips on dropping the engine so hopefully that alone will help a few out



Provisionally secured a Gasgas EC300 which should be collected Friday, then I can have my first real look/head scratch at how to make it work, certainly not going to be a 2 minute job lol..

These bikes are built in Taiwan not Japan...... so the expectation of quality you would get from the name on the side is out the window so to speak. They're decent for what they are though

Here's a 250 2t build (maybe one of the first on this forum) for inspiration. I have seen it done both with and without modifying the frame, just depends on the extent of the work you want to do I guess..... 2-stroke 250 Grom build!

 

[shush319]

These bikes are built in Taiwan not Japan...... so the expectation of quality you would get from the name on the side is out the window so to speak. They're decent for what they are though

Here's a 250 2t build (maybe one of the first on this forum) for inspiration. I have seen it done both with and without modifying the frame, just depends on the extent of the work you want to do I guess..... 2-stroke 250 Grom build!

And another with a Quad Racer motor: Quadracer Motor (another boring 250 swap)

 

[Jamesstone]

Thanks for that @shush319

Just watched the first one's series on YouTube, looks like he got it all running but never really continued with the blogs sadly on YouTube - Good insight and I'm on a similar thought process with using the original rear engine mounting point (hoping to avoid chopping the standard frame and having to tube it) by tilting the engine forward which he suggests in his first video

Certainly have my work cut out for me

 

[Jamesstone]

The donor has arrived!

2002 KTM EXC 300 collected today, had over £1,300 spent on the engine 2 years ago so hopefully get a few runs out without it going pop lol! cheap enough bike so certainly not mint but perfect for the project

 

[Jamesstone]

KTM stripped and test fit completed!

Its been a busy week for the project, the weekend consisted of stripping the EXC300 down to the ground, even with a wash before dismantling its amazing how much mud was still buried around the bike but pleased to report it all came apart nicely enough!

First look at the engine in the Grom frame, straight away I realised the stock upper engine mount was going to need to be chopped off to let the engine go back far enough whilst maintaining a good front sprocket height.

Loom stripped down and the frame bracket chopped off, wasn't looking to bad in place (better than expected) but a custom exhaust will be required to increase clearance for when the forks compress and to route round the rear subframe and out the back.

Sprocket lined up well, the height is a slight concern but will come back to that later..

Marked the from frame in preparation for utilising the KTM cylinder head mount (this was perfect to start squaring the motor up to design the rest of the mounts)

Also quickly fitted the side fairing, almost like it was built for a kick start! the brake pedal clears and the gear lever also sits perfect the only real issue at the moment is the carb which I think I may have a solution for but time will tell (wish I was decent at design/3d printing)

 

[shush319]

Nice work. Love seeing projects like this progress.

I have a KTM 390 Duke & have often threatened to swap in a big 2T if the engine ever let go. Have now done a bunch of mods to it & that thing is pumping out nearly 50hp to the wheel, with 40ish ft lbs of torque, so I have decided on a rebuild if it does go.... LOL

 

[Jamesstone]

Yea the 2 stroke won't have that amount of torque, the Duke 390 is a cool bike (briefly took one out a few years ago) the Grom just needs more "punch" so hopefully I will achieve that with the KTM lump

 

[Jamesstone]

First look at the engine mounts

I had a quick look at options for engine mounting today, I had originally planned to use steel tube welded to the Grom frame but due to my limited welding ability and concerns on how easy the engine would be to remove for servicing/rebuilding I'm swaying towards 5mm laser cut steel plates either side for the front cradle and rear mounting point.

Quick look with some cardboard to put some ideas into place (the top half near the from frame still needs some figuring out)

The rear will also require two but with some spacers to correctly place them against the original Grom frame mounting points, the big question is will it be strong enough (I think so is my answer - famous last words)

 

[Jamesstone]

Final version of the engine mounts completed in cardboard/acylic

The plan this weekend was to make the final draft for the engine mounts, happy with how they have turned out as this also means its easy to remove the engine for servicing if/when required.

First look at the rear one in place, this again will make more sense once all the spacers have been machined.

The finished cardboard templates to post off to my friend to hopefully have them transferred into CAD so that the chosen laser cutters can complete some clean cut mounts for me.

I "think" I may have found a solution for the carb mounting without chopping the frame, should hopefully know this week once parts begin to arrive.

Also a few more videos on the series are now live on the channel :

 

[Jamesstone]

The Carb is on!!

A little more progress on project Hoonigrom today, the Carb is on without cutting the main frame! I did have a thought that silicone may not be suitable to retain its shape with the vacuum with the running engine even at 6 ply so it will be swapped out for aluminium tube and cut to the same shape if I experience any running issues but happy to see some progress.

Also managed to get a nearly new CBR250/300 radiator, looks like its going to be a good fit for the space where the standard airbox once sat.

Purchased some handle bar mount adapters from eBay so that I could fit the fat/wide buys that came with the EXC, much nicer than the skinny stock ones and as I won't be commuting or filtering the narrow width of the stock bars is not required. Long term plan will be to get them all painted black as I'm not a fan of the bright anodised colours..

 

[Jamesstone]

A few more updates & the next video now live!

I helped a friend with sourcing a bike recently and as a thank you he kindly got me a jacket made for the project, really chuffed with it!

Renthal grips fitted and the original clutch master cylinder and line from the EXC 300 bolts straight on with the hose being the correct length which was is awesome

Its now a waiting game for the engine mounts, problem with it being a favour is you can't push for it to be done but I'm sure it will be worth the wait rather than cutting them out free hand.

A small digital thermostat also arrived, £15 off eBay which will allow me to keep an eye on the water temps

Started working on the wiring too, going to hopefully use the left hand switch gear from the Grom in order to have indicators working as factory.

Next video now also live on the channel

 

[shush319]

I saw a video on the Honda Grom Fatherz FB page by Kenny. When I saw this rad & kind of how he mounted it with a CBR300 swapped Grom I though of your project.

 

[Jamesstone]

saw a video on the Honda Grom Fatherz FB page by Kenny. When I saw this rad & kind of how he mounted it with a CBR300 swapped Grom I though of your project.

Thankfully with the 2T engine I have plenty of cylinder head space compared to the 4T conversions, big progress push today which I'll share with you all shortly but in a nut shell the wiring loom is in and we have spark!

I'm in the process of swapping the Grom headlight over to the EXC300 loom and to be honest the head light is baffling me even with a wiring diagram! any members help identify?

Basically I have the following on the EXC plug (pretty straight forward) negative, low beam positive & high beam positive. The 2017 grom headlights has 6 cables, I "think" I have worked out the below but don't fancy popping a headlight if some one has any input?

 

[shush319]

Thankfully with the 2T engine I have plenty of cylinder head space compared to the 4T conversions, big progress push today which I'll share with you all shortly but in a nut shell the wiring loom is in and we have spark!

I'm in the process of swapping the Grom headlight over to the EXC300 loom and to be honest the head light is baffling me even with a wiring diagram! any members help identify?

Basically I have the following on the EXC plug (pretty straight forward) negative, low beam positive & high beam positive. The 2017 grom headlights has 6 cables, I "think" I have worked out the below but don't fancy popping a headlight if some one has any input?

This may shed some light on the situation..... See what I did there? LOL

2018 Grom Wire schematic

Can anyone send me a copy of the wiring schematic for a 2018 Grom. I need to find out what each of the colors that go to the headlight do. I'm trying to fit the Grom headlight to another bike and need to know what wire goes where. Thanks a bunch. Rdub

www.hondagrom.net

There's also a SF harness to h4 adapter here that if you could find someone with one that would be kind enough to take pics of, may also help.

 

[Jamesstone]

I see what you did there @shush319

Thanks for the link, had a good read through the post and I think its confused me more than before LOL!

The guides seem to detail going from the Grom loom to an aftermarket headlight, you would hope it would simply be the reverse of that to power up the stock headlight but I don't think it is looking at the pictures they have included, would be rubbish to blow out a working LED headlight so will need to do some more research before putting a 12v battery to the cables (thankfully it doesn't appear to run AC current like the original Grom headlight)

 

[Jamesstone]

Another big push on project Hoonigrom!

It feels like things are really coming together now (famous last words) yesterday I managed to put a good few hour in and happy with how its all fitting up, like all projects there are things I'm discovering and having to order as I go but the below was good to see.

I'm currently waiting on the first batch of custom spacers for the engine mounts, machine shop is not an over night process so I have utilised some M6 stud and nuts for the coil pack for the testing stage. As advised in the beginning of the series the plan will almost be a rough build, make sure it works and if so strip it all back down in the winter to revise and send away for the full paint as there is a good chance I will encounter issues and it will need pulling back apart.

I originally though the speedo on the KTM was broken and was a cheap aftermarket one, turns out the Sigma Sport for motorcycle range are not cheap Chinese rubbish and simply needed a new battery to get it working again. I plan to use the ABS sensor location to mount the Sigma sensor.

The custom line arrived from HEL performance, ordered Saturday and arrived Tuesday - Great service! this allowed me to delete the ABS and use the KTM/Brembo master cylinder with the Nissin stock brake calliper (no doubt big brake kit will be required shortly)

Still awaiting a response from the custom exhaust builder but as the stock one was already damaged I "massaged" it to clear the front wheel for start up/testing as it was already heavily dented & bent

Wiring loom in place and the radiator return line cut to size, the supply line from the head has some tight bends and caused the hose to pinch so I've ordered some pre-formed silicone hoses to improve the run.

Radiator drilled and the temp sensor installed using JB weld, it's actually set really smoothly this morning and looks much cleaner than the below picture (thankfully)

First look at my new dashboard layout, put the remaining 5mm black acrylic to good use, not 100% sold on it so will revisit it again but works great for speedo & keeping an eye on water temps.

Small fly screen, again needs some more time really getting this how I want it too look

I wired the kill switch into the original Grom key so that when parked I can lock the steering and kill the ignition, just a little security for when parked but not that I ever really plan to let it out of my sight as these are easily lifted/stolen.

Good news! I removed the spark plug and gave it a quick dry kick and we have spark so looks like the wiring all works, now just a case of getting all the stock Grom lights/indicators figured out.

 

[shush319]

Very nice.