Forum Donations
Search
VTF Google Search
 Click Here

Big bore

  • Advertisement

Post a reply

Big bore

PostAuthor: Lawbreakingtrucker » Fri Aug 25, 2017 2:25 pm

I've read threads 6 and 7 years old threads about big bore for the 250 engines..
Do any of You guys still ride these bikes and did the engine modifications work for a longer period of time?
I've just got my first bike this year and I love to work on it in my garage. This winter I will give it some more power and I'm looking into making it a 280cc engine. If any of You guys that tried this in the past will point me in the right direction I would appreciate it a lot.

My plans for the bike is inspired by Larish41, bigger homemade exhaust (1-3/4"), 52mm pistons (280cc), maybe bigger carburetor and changing the sprockets to 17/40.

Any thoughts on this for my clonebike? Jinlun Spartan JL250V
retsis ti esool ro ti evoM

Lawbreakingtrucker
Junior Membership
Junior Membership
 
Posts: 7
Joined: Sat May 27, 2017 1:18 am
Location: Fall*star, Denmark Flag
Bike year & model: 2008 Chinese 250 V-twin
Sex: Male

Re: Big bore

PostAuthor: Lawbreakingtrucker » Fri Oct 13, 2017 11:40 am

Anybody who can help me with wich pistons that will fit the 2V49FMM engine. I wanna go up to 52mm but dont know wich other dimensions the piston needs.. and from wich other engine can I use the piston.
retsis ti esool ro ti evoM

Lawbreakingtrucker
Junior Membership
Junior Membership
 
Posts: 7
Joined: Sat May 27, 2017 1:18 am
Location: Fall*star, Denmark Flag
Bike year & model: 2008 Chinese 250 V-twin
Sex: Male

Re: Big bore

PostAuthor: eslmatt » Fri Oct 13, 2017 7:47 pm

Seems like you have some fabrication skills :bg: or are at least willing to learn.

I have an xv750, but also a Chinese 110 that I over-bored to 125 (with a kit)

This particular bike was not popular in China, so there is no aftermarket big bore kit. I checked. If they used a Jl110 piston. (Chinese copy of a Honda Super Cub) it will be easy to fit a larger piston 52mm. It may get a lot more complicated if not. The hardest thing is finding measurements on replacement pistons.

One of the most important measurements is the wrist pin to top of piston. This will alter your compression even a 1 or 2 mm off will make a big change.

So, when your riding season is done, pull the engine apart and get the piston out. Search for piston measurements on 125cc engines. If you are very lucky someone will have done this upgrade.

When you figure it out, post it here and have the mods mark it (solved) it will help the next person doing this.
1984 VX750 Japanese special - stolen - RECOVERED
build thread -> http://viragotechforum.com/viewtopic.php?f=32&t=58187&sid=e4ab82933609aa211c1efb06cf000508

2010 Jailing 110 customized

Image
When asking how, also tell me why.

eslmatt
Senior Membership
Senior Membership
 
Posts: 383
Images: 26
Joined: Wed Jun 11, 2008 9:05 am
Location: Jilin, China Flag
Bike year & model: 1986+ xv750 Japanese special
Sex: Male

Re: Big bore

PostAuthor: JrZook » Wed Oct 18, 2017 4:49 am

Didnt see this post until now. Ive been running the 52.4mm bore for near 2 years and around 10k kms. No issues at all! These are the pistons ive been running http://www.miniatureparts.co.uk/index.p ... uct_id=924
I did have the crowns ceramic coated and the skirts teflon coated for extra insurance but I do also run advanced ignition timing, twin carbs and srv250 cams which gets me around 26hp at the wheels.
This bike get daily driven to work and back then out for runs every now and then on the weekends
Engine Specs:___________________________________Bike Specs:
HE 285cc_______________________________________FZR250 twin disc front end
52.4mm ceramic/teflon coated flat top pistons_________GSX600F handle bars
Wiseco TTR125 intake/exhaust valves_______________Relocated rear shocks
TTR125 valve springs_____________________________17/40 sprocket
Ported heads, 3 angle seat cuts_____________________XV700 Tacho
SRV250 cams on custom needle roller bearings________Metzler Lazertech tires
Twin Mikuni BDS26 carbs__________________________Custom 2-1 exhaust
Lightened rotor__________________________________Harley sportster muffler
XT250 clutch pack
User avatar
JrZook
Silver Membership
Silver Membership
 
Posts: 1388
Images: 4
Joined: Mon May 11, 2009 10:49 pm
Location: Brisbane Flag
Bike year & model: '94 XV250 Sui-Cycle!
Sex: Male



Post a reply


  • Advertisement

Return to Yamaha Virago clone bikes Quinjang Lifan Delta ....

Who is online

Registered users: Baidu [Spider], faffi, Flyingdog, Google [Bot], harrybb1991, Hellgate, Jeff0133, Majestic-12 [Bot], NikNacz, Yahoo [Bot]