300 EC Supermoto conversion informations

[Antoine]

Hello Everyone !

I am new to this Forum and pretty surprised to see the success of Gasgas bikes all around the world !
To introduce myself briefly, I am a 24 year old French dude and I've been riding Gasgas bikes in the past but trial ones.
My new (and first) job brought me here :



If you zoom in, you'll discover a wonderful playground around the mountains. It would be a shame to not be riding here !

I've always had this old dream of a big two stroke supermoto on the road (the best bike I had was an Aprilia 125 MX with the Rotax engine) but I never took the step. Shame that the road legal 500 CR became quite pricy !

After serching for a while, I found that the Gasgas 300 EC could be the perfect fit. And I'd still have the possibility to switch back to enduro wheels and have fun in the dirt.

However, to use this bike on the road, I would need to know which rims can I adapt.

I've read a lot of posts about this subject but I couldn't find any actual dimensions. I even sent an email to Gasgas but didn't get any answer.

The idea here would be to get 17" wheels adapted easily without having to buy the 1000€ Gasgas ones :

http://www.motocrosscenter.com/shop...rd-gas-gas-17x350-y-17x425-be55400sm2510.html

So, if you guys could help me to sum up which rims from other brands can be adapted without mods that would be great.

If there is no precise list, the other option is to get the dimensions that have to be checked when buying a used set of rims.

I am looking for a GasGas model after 2007.

Could someone provide me those infos ? (Just ask me and I'll make a drawing of what I exactly need)

- Wheel axles diameters. I have been reading that the diameter changed somewhere in 2004. I think it is 20mm at the rear and front. Other brands may have 22mm or 25mm so this could be a problem.
- Width of the wheels hubs (from one bearing to another)
- Dimensions of the discs supports
- Dimensions of the rear sprocket support
- Width from the disc support to the sprocket support
- Width from the sprocket support to the next bearing

Or could life be easier : who managed to adapt a set of rims from another brand without modifications ?

Someone from this forum (Gassergrant) adapted CCM wheels without much mods, so I guess those wheels could be found on other bikes ?
Here is the thread : http://www.gasgasrider.org/forum/showthread.php?t=16956

I found the max width of the rims : 4.25 for the rear and 3.5 for the front.

For the rear tire, I found the info as well, it is 150 maximum, otherwise it will rub the swingarm.

The second point seems to be a big matter to me : the front chain sprocket.

Using such a bike on the road will require to adjust the transmission. The stock front sprocket being a 13 teeth, can I switch to a 15 without grinding the hydraulic clutch module ?

And why not a 16 ? Who would be able to give me some feedback of the right ratio to use with 17" rims to cruise comfy on the road at normal speeds ?

The 15 teeth is available here : https://www.3as-racing.com/A-242503-pignon-acier-jt-gasgas-200-250-300-400-450-cc.aspx#.V1RyEUtu2Qs

I remember about reading some posts from Jeff on this forum. Jeff if you're around, do not hesitate to share your experience / feedbacks

Any other info about SM conversion on a 300 EC is welcome !

Btw, is there a key on post 2007 Gasgas ? I think there is a lock on the fork but no "ignition" key ?

Thanks a lot guys for your feedbacks and answers !

Greetings from France.

Antoine

 

[hadfield4wd]

Welcome. Where? My daughter is in France now on an internship. In St. Lo.

 

[pscook]

Keeping it short - Ignition switch is present on any of the EC300 with electric start, or you can install a switch into a non-e-start wiring loom if you have the capacity, or swap the non-e-start loom with an e-start wiring loom.

15 tooth CS sprocket won't fit, as a 14 tooth barely fits. I have a 2011 EC200, but the cases are the same from 2005 and up. If someone says a 15 will fit, I would like to see pictures and understand exactly how they installed the sprocket, short of removing the motor.

Regarding wheels: Warp 9 here in the states would be a good resource, they might be able to set you up with proper wheels for less than 1,000 Euro. Otherwise, expect to perform some sort of modifications to wheels or bike to get an off-brand set of wheels installed.

Good luck!

 

[Antoine]

Welcome. Where? My daughter is in France now on an internship. In St. Lo.

In south west near Tarbes. St Lo is quite far away !

Keeping it short - Ignition switch is present on any of the EC300 with electric start, or you can install a switch into a non-e-start wiring loom if you have the capacity, or swap the non-e-start loom with an e-start wiring loom.

15 tooth CS sprocket won't fit, as a 14 tooth barely fits. I have a 2011 EC200, but the cases are the same from 2005 and up. If someone says a 15 will fit, I would like to see pictures and understand exactly how they installed the sprocket, short of removing the motor.

Regarding wheels: Warp 9 here in the states would be a good resource, they might be able to set you up with proper wheels for less than 1,000 Euro. Otherwise, expect to perform some sort of modifications to wheels or bike to get an off-brand set of wheels installed.

Good luck!

Thanks for your answer.

Given that the bike will be between 2007 and 2010, it will not be an e-start so I will have to install a key.

Here he says that the sprocket is 15 teeth : https://www.youtube.com/watch?v=tPQ0j-2uGRw

Antoine

 

[Anders]

My son built a SM version of his 08 model 300. He was lucky enough to find a set of GG wheels locally.

I have not heard of other wheels that fit right in without modifications, but (almost) anything can be made to fit if you have access to a lathe and a milling machine

In general the front wheel will be pretty easy to do, while the rear is more difficult as you have to search for a wheel with (almost) the same distance between sprocket and brake disk as the originals.

I have several wheel sets for my bikes so I can make any measurements you need. I can do it this week, but am quite busy so it may take a few days.

I have done wheel conversions on other bikes (fitted a set of PVM magnesium rims intended for a Ducati TT2 to my Bimota Supermono) so I know what it takes.

Depending on what you find on the secondhand market, I think you'll eventually find that the wheels from Motocrosscenter actually are quite affordable. Remember that the price includes disks and sprocket and even tires.

Regarding the front sprocket I don't really see the point in going bigger than 14, as there are plenty of smaller rear sprockets available.

 

[Antoine]

My son built a SM version of his 08 model 300. He was lucky enough to find a set of GG wheels locally.
http://www.gasgasrider.org/forum/picture.php?albumid=101&pictureid=871
I have not heard of other wheels that fit right in without modifications, but (almost) anything can be made to fit if you have access to a lathe and a milling machine

In general the front wheel will be pretty easy to do, while the rear is more difficult as you have to search for a wheel with (almost) the same distance between sprocket and brake disk as the originals.

I have several wheel sets for my bikes so I can make any measurements you need. I can do it this week, but am quite busy so it may take a few days.

I have done wheel conversions on other bikes (fitted a set of PVM magnesium rims intended for a Ducati TT2 to my Bimota Supermono) so I know what it takes.

Depending on what you find on the secondhand market, I think you'll eventually find that the wheels from Motocrosscenter actually are quite affordable. Remember that the price includes disks and sprocket and even tires.

Regarding the front sprocket I don't really see the point in going bigger than 14, as there are plenty of smaller rear sprockets available.

Hey Anders !
Thanks for your thorough reply.

I do have access to a lathe so I can do bushings and things like that. The idea is that I just don't want to spend 2 months on it if it's too much work ^^

Thank you for your proposition, that's very kind ! I'll let you know which measurements I need if I go and check some wheels.
As you can see in this example : https://www.leboncoin.fr/equipement_moto/972492076.htm?ca=16_s (this is our "Gumtree" haha), even with brand new tires, I can get a set of rims for half the price of new ones. And they'll do the same job !

For the sprocket, I was a bit afraid that a small rear sprocket could eventually get the chain to touch the swing arm or the chain guide. Any thoughts about this ?

Thanks a lot

Antoine

 

[slocalspode]

Antione, you seem to be well on your way gathering information.
I took the easy, and safe way. I sourced a set of stock enduro
wheels for my SM project. I used the stock wheel hubs and had a
local wheel house, (Buchanons), lace up a set of Excel rims with
their spokes and nipples.
As for the 15 tooth. I had some trouble getting the 14 to fit on my
bike. I had to remove the swing arm pivot bolt and move the swing
arm back to get the sprocket past the plastic swing arm slider.
Also I had to grind ~1mm from the clutch master too.
There is a picture somewhere in my earlier posts.

I have *heard* that Husqvarnna wheels from certain years are a direct
bolt on replacement for the GG wheels. Again you will need to measure
the axle diameters and hub widths to be sure.
This is why I bought used stock hubs. So much easier.

Finding the 320mm brake rotor and caliper offset bracket could also cause
some problems. I got lucky and found a stock GG rotor sitting on a dealers
shelf. I think the offset bracket was from Motomaster and was for a KTM
with the same Marzocchi forks and Brembo caliper. It took some research.

All in all the effort was worth it. the bike is a hoot to ride as long as the
highway speeds are kept below 100kph. The bike will run higher, no problem,
but the bike has that 2-stroke surge as the power valve opens up right around
that 100kph speed. it wants to GO!!! from there.

Good luck and keep us posted on your progress.
Jeff

 

[pscook]

I just remembered that I was told that a mid-90's KX250 wheel bolts right into the GG swingarm. I'll have to find the person who told me this and have him pop into this thread. If it's true, then you could look for an aftermarket KX250 SM wheel, if it exists. Or do what slocal mentioned, lacing a set of rims to GG hubs, then sourcing the front rotor conversion through research and parts bins.

 

[Antoine]

Antione, you seem to be well on your way gathering information.
I took the easy, and safe way. I sourced a set of stock enduro
wheels for my SM project. I used the stock wheel hubs and had a
local wheel house, (Buchanons), lace up a set of Excel rims with
their spokes and nipples.
As for the 15 tooth. I had some trouble getting the 14 to fit on my
bike. I had to remove the swing arm pivot bolt and move the swing
arm back to get the sprocket past the plastic swing arm slider.
Also I had to grind ~1mm from the clutch master too.
There is a picture somewhere in my earlier posts.

I have *heard* that Husqvarnna wheels from certain years are a direct
bolt on replacement for the GG wheels. Again you will need to measure
the axle diameters and hub widths to be sure.
This is why I bought used stock hubs. So much easier.

Finding the 320mm brake rotor and caliper offset bracket could also cause
some problems. I got lucky and found a stock GG rotor sitting on a dealers
shelf. I think the offset bracket was from Motomaster and was for a KTM
with the same Marzocchi forks and Brembo caliper. It took some research.

All in all the effort was worth it. the bike is a hoot to ride as long as the
highway speeds are kept below 100kph. The bike will run higher, no problem,
but the bike has that 2-stroke surge as the power valve opens up right around
that 100kph speed. it wants to GO!!! from there.

Good luck and keep us posted on your progress.
Jeff

Hello Jeff,

Thanks for coming along ! Your last words brought my motivation to a even higher level !

I dropped too early the idea of having stock GG hubs laced on Excel rims but it actually may be a very good option. I will check if my local bike shop would do that for me, and at what price.

I have to see that picture of the grinded clutch module. I would not be very happy to do so? And imagine what should I have to do with a 15 teeth sprocket. Maybe impossible ?

Yep, I'll keep everyone updated about this project.

I just remembered that I was told that a mid-90's KX250 wheel bolts right into the GG swingarm. I'll have to find the person who told me this and have him pop into this thread. If it's true, then you could look for an aftermarket KX250 SM wheel, if it exists. Or do what slocal mentioned, lacing a set of rims to GG hubs, then sourcing the front rotor conversion through research and parts bins.

Hello pscook,

Thanks for sharing this info. It could be useful.

Cheers guys,

Antoine

 

[slocalspode]

This help?
you can not see where I had to grind the master, but, you get the idea.
It was not very much material. It is rather thick in that area.
Notice the sprocket behind the plastic swing arm guard.

I am using a 40 tooth rear from a Husky I found on E-bay.

 

[Antoine]

http://i288.photobucket.com/albums/ll172/SloCalSpode/EC250SM/EC250SM-10.jpg

This help?
you can not see where I had to grind the master, but, you get the idea.
It was not very much material. It is rather thick in that area.
Notice the sprocket behind the plastic swing arm guard.

I am using a 40 tooth rear from a Husky I found on E-bay.

Yep, this helps. Thanks for the picture. I can see that it is quite tight around here?

I keep you informed as soon as the project moves forward or if I need some info in order to go and check used wheels.

Thanks everyone.

 

[stian]

Having sm converted my own 300 I can tell you how I feel about this. My 300 is with the wheels you linked to, with Brembo gold brakes from an old ducati up front, std rear. 13-40 gearing. If you have the standard 45 zooks, you can order some new springs right away. Front braking makes the front forks hit bottom pretty easy.

Max gearing that you can find and fit on these bikes are around 14-40 or if your lucky, 14-38. Still makes commuting a bitch.

If you live in the city its OK. If you have roads where you can hit 70-80mph / 140kmh I would choose a bigger fourstroker.

Btw, 4,25 rear looks a bit thin and stupid. Does it job thought.

 

[Antoine]

Having sm converted my own 300 I can tell you how I feel about this. My 300 is with the wheels you linked to, with Brembo gold brakes from an old ducati up front, std rear. 13-40 gearing. If you have the standard 45 zooks, you can order some new springs right away. Front braking makes the front forks hit bottom pretty easy.

Max gearing that you can find and fit on these bikes are around 14-40 or if your lucky, 14-38. Still makes commuting a bitch.

If you live in the city its OK. If you have roads where you can hit 70-80mph / 140kmh I would choose a bigger fourstroker.

Btw, 4,25 rear looks a bit thin and stupid. Does it job thought.

Hello Stian,

Thanks for the precisions. What do you mean by "Still makes commuting a bitch" ?
I will mostly ride below 140 kph (I live in the mountain).

Cheers

Antoine

 

[WAZ]

You can go as small on the rear sprocket as the hub will allow, I ran a 35t rear without the chain run causing problems. I also fitted lower uprated springs, Brembo 320mm disc and 4 piston caliper, and a Magura front master cylinder. I don't recommend fitting Aprilia RS125 wheels, they are a lot of work to fit, but it shows thay almost anything is possible.

 

[Antoine]

You can go as small on the rear sprocket as the hub will allow, I ran a 35t rear without the chain run causing problems. I also fitted lower uprated springs, Brembo 320mm disc and 4 piston caliper, and a Magura front master cylinder. I don't recommend fitting Aprilia RS125 wheels, they are a lot of work to fit, but it shows thay almost anything is possible.

Hey WAZ,

Thanks a lot for those useful infos. That's good to know since I was afraid to end up with a too short geared bike once on the road.
I'll let you guys know as soon as I'll start the project.

Antoine

 

[Harry]

Hi WAZ,

The extra effort to fit those RS125 wheel was worth it. They look great.

Now where could I find a RS125 donor??

 

[Antoine]

Hi WAZ,

The extra effort to fit those RS125 wheel was worth it. They look great.

Now where could I find a RS125 donor??

Pretty much everywhere here : https://www.leboncoin.fr/equipement_moto/994445976.htm?ca=16_s

 

[Harry]

Thanks, Antoin

But I am stuck in the South Pacific Workers Paradise (NZ) and RS125 are not very common.

 

[Antoine]

Thanks, Antoin

But I am stuck in the South Pacific Workers Paradise (NZ) and RS125 are not very common.

Haha sorry man, thought you were in UK or some country in Europe... But lucky you to live there Just a shame it's so far away (as my old NZ English teacher told me once)

 

[motopsycho87]

I've got a gs500 rear and a tzr125 front.

I had to turn down the outer diameter of the front disc to fit, then found bearings to suit.

The gs500 rear, same on the disc, but I also had to skim the thickness too, the inner clearance had to be filed out (could be drilled... I was in a rush!), then bearings to suit, and made spacers for both. The gs500 sprocket needs countersinking, as the nuts otherwise protrude and hit the swingarm. Currently using continental contitwist sm, would recommend the sport compound. If you need any measurements or pictures, pm me