Big bore kit for a YBR.

[Kieron2013]

I've got a 2009 Yamaha YBR 125 ED (with efi), and I'm getting my A2 soon. I am looking at getting a bigger bike, but I would also like to put a sidecar on my YBR. The standard engine may not have enough torque or power to manage most road speeds, would it be possible to fit a 150 or a 180 big bore kit and what other modifications would need to be made, and would the reliability be compromised by the engine modifications. P.S. I have a budget, I have worked out what I can afford, and I cannot afford two bigger bikes, even if I sell my YBR. I know it will not be fast, I don't care. I am doing it because I can't afford to run and insure a car but I need to carry stuff. I will have the work done by a capable mechanic, but I understand that he may not be the most reliable source of information regarding reliability.

[raesewell]

Big bore

[Guest]

how about a bigger bike with a trailer and ditch the ybr all together

[Westbeef]

https://www.ebay.co.uk/itm/Big-bore-150cc-Barrel-and-piston-kit-upgrade-for-Yamaha-YBR-125-2009-/311720944587

but to be honest I wouldn't faff putting a sidecar on, that's surely going to cost hell of a lot more than buying a bigger bike with more storage?

[Kieron2013]

I know someone who can make a custom sidecar fairly cheap. My bike is worth about £50, if that. It will not cover the cost of another bike. I'm not doing it to be a serious day to day vehicle. It's to carry bits and pieces. I only want to know about the facts on big bore kits.

[fastbob]

Are you thinking of carrying a passenger in this sidecar ? Anyway there are plenty of big bore kits available at ridiculously low prices . Obviously they are made in China but so are YBRs for that matter so you do take a chance on the quality. If you are going to ask a 125 to haul a sidecar you will have to change the gearing and sacrifice quite a bit of speed . Have you considered how exactly you are going to attach a sidecar to a bike that doesn't have much of a frame to bolt to ? It's also worth considering changing the tyres to square profile ones so that's another expense. I also know that sidecars need to be very carefully set up to make the outfit handle safely so some form of adjustment needs to be incorporated into any design . Then there are bound to be a mass of mot regulations to look at but I don't have any idea about that . Lots to think about but an interesting idea.

[fastbob]

Here's some inspiration

[Kieron2013]

I have looked into it. The YBR isn't a fast bike to begin with but I'm confident that it could push on to 40+ mph (without a big bore kit), which is enough for my intentions. I've consulted a mechanic who has some contacts in other industries (welding, powder coating, and fibreglassing). He has suggested the big bore kit but he advised that I do a bit of research on reliability, as he generally refuses to modify bikes. I am well aware that reliability will suffer, but I was wondering about the capabilities of the crank shaft and the bottom end, rather than anything else. I am confident that the bike can pull the weight as standard, but more power and torque will be useful. The sidecar is going to fit to the down tubing in front of the frame, the rear section of the frame (just behind the engine), and the tail section. It will be designed to carry passengers, and it will be set up to handle properly, although I've been told that the majority of handling problems occur at 50mph+ so that shouldn't be too much of a problem. The sidecar isn't covered on an MOT, as it's classified as a modification, much like a tow bar on a car. However it will be well maintained. As I said before, the bike is only worth about £50 so I won't have lost a great deal if it doesn't work out.

[Kieron2013]

I was also wondering about the choice between a 150cc and a 180cc big bore kit, with regards to reliability and torque output.

[Mr Fro]

I commend you on your daring and you should totally stick a thread up about the conversion!

If you're going to do it then you might as well go all in and stick the 180 on it. So long as the compression ratio doesn't go much above standard then you shouldn't have too much trouble. Yes you will probably lose a bit of longevity from the bottom end but you could get round that to some degree by having the crank/piston assembly balanced.

My concern would be the sidecar - my 125 frame is a wobbly little thing at the best of times and having *insert weight of sidecar here* hanging off the side won't help it much.

Mind you, if it does end up flexing like a good 'un you could always beef the frame up.

[oldgrump]

Hi, just to let you know, the sidecar when fitted will need a MOT, yes as you say it is as a bolt on, but it will still need a MOT. I've included a link, but setting up chairs is a work of art, and I think [mention]fastbob[/mention] said, you may have to look at changing tyres as well. here's a link http://www.steves-workshop.co.uk/vehicles/bmw/sidecar/sidecaradjustment/sidecaradjustment.html.

And another http://www.steves-workshop.co.uk/vehicles/bmw/sidecar/legal/sidecarlaw.html

[Kieron2013]

I was expecting the frame to need a bit of reinforcement,to be fair. Also, thank you for telling me about those sidecar laws. I was unaware of them, and I had been told that it was an accessory, not a part of the vehicle. I am going to create a new thread when I start the project, and I will keep you all updated on progress. Hopefully it will be done by the end of June, so I'll be taking it to the Great Yarmouth Motorcycle Takeover on July 7th, if possible.

[Chrissb6]

Big bore kit just the start of it. Have you considered the rest of the motor? Additional loads on the clutch gearbox and final drive. This bike and its running gear was built for a specific task, as a lightweight commuter, l personally feel your going to spend a lot of time and money and end up disappointed. Better to go large l would say.

[Kieron2013]

I have looked into it. I have done some research. It is why I am using a YBR. They are used in asia to move more than just a sidecar, and I am happy that it will manage, even if it needs repairs more often. I am not getting 2 larger bikes because I will not be able to afford the insurance.

[Guest]

Deffo would like to see a build thread. Interesting project. whatever the difficulties I hope you pull it off.

[megawatt]

Yes, this will make a great build thread and respect to you for being brave enough to even think of doing it. I assume you've already considered lowering the gearing to give you more bottom end torque as you don't need top end speed?

[Kieron2013]

Yes, I will be lowering the gearing as well as some other modifications. I was also considering a shaft drive conversion too, but that might be a bit too costly.

[TimR]

Why not look for a ybr250 ? If your set on using a ybr .

The strain on a bigbore kit will rapidly wear engine components

http://r.ebay.com/8deV9h

[Kieron2013]

I have looked for a 250. I don't wish to spend nearly £2k to buy one, and the only ones cheaper than that are FUBARed.