Lifan 150cc big-bore kit: Installation

Racing Ruben

Active Member
Hey guys,
I'd just like to give a big (bore) thank you to everybody who added hints and tips on this topic, especially to Crazy.
Thanks to this piece of information I succeeded to install my kit without any problems. One moment of panic when I dropped one of the pushrods in the engine but I got it back pretty quick.
It started from the first time (same carb settings as I had before: 48-95 jets and velocity stack) and rode it for a few k's. Sounds great, feels great! Very curious to see how it performs in a few 100 km's.

A very grateful and proud Ruben
 

2b

Been Around the Block
Racing Ruben said:
It started from the first time (same carb settings as I had before: 48-95 jets and velocity stack)

Well done Ruben. Good to hear another success story.

Were those jets both from OO Racing? If so then I think that they are probably pretty much optimal when you look at what I had worked out in here...
https://docs.google.com/spreadsheets/d/1USvziYIyzfyxfZA1YYpQf9eP4djb0GLWbvWcmME88Gk/edit#gid=1

Once you get it run in, if anything is not right at wide open (running a little rich?) you could try a 92.5 in the Mikuni (9mm) sizing or 100/102 in Keihin (8mm) sizing

Oh and where did you get the velocity stack for the standard carb from?

Cheers
Richard
 

Racing Ruben

Active Member
Hey Richard,
Great document. I read it carefully. It's a fantastic summary. All you need to know to tune the carb on our aces.
The pilot jet I'm using comes from the rejet kit from OORacing. The main jet and the velocity stack was bought in a local store.
http://www.antwerppitbikestore.be/
It wasn't cheap but the pod filter was choking my engine after the first rejet and the bigger header. The stack works great. I put a wire mesh in it to prevent sucking in small birds and other stuff ;-)

I tried a 100 main jet for a while but it sputtered at WOT.
Maybe I shouldn't mess with the jets until the engine is completely run in?

I'll keep you guys informed.
 

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2b

Been Around the Block
Yep leave well enough alone until you can run it hard. If it ain't broke, don't fix it :)

When you do pull the main out, it would be interesting to know whether it is 8mm or 9mm long, that seems to be the distinguishing factor between keihin and mikuni sizing. I see the shop sells both. It's pretty obvious but as I mentioned in the write up you need to be sure that you are only changing sizes of main jet not manufacturer when sorting the main.

If it is 9mm long then it is a mikuni jet and you may find that tests show you are running a little rich and you could go down to a mikuni 92.5 (you certainly wouldn't want a 100 mikuni in there)

If it is 8mm long then it is a keihin jet and you may find that tests show you are running a bit lean and you could experiment with keihin 98 or 100

Did you get the first stack on the "open air tunnels" page? i.e. "Open Air Tunnel 40mm Silver - Long"

And what did you use for mesh and how did you attach it?

Cheers
Richard
 

Racing Ruben

Active Member
I'll defenitely check the length of my main jet next time. Thanks for the info.
The stack is on the website under "air filters " then "air tunnels open"

A bit embarassing but I used a part of a tea infuser spoon I had in the kitchen. It was just the right size. I placed it all the way in the stack, close to the carb opening. Its squeezed between the stack and the carb.
 

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Racing Ruben

Active Member
Checked the length of the main jets I'm using. They're 8mm keihin jets. At the moment I'm using a 48 pilot, 100 main combination, velocity stack,OORacing header, trumpet muffler with minimal dampening wool, and big bore kit.

A bit unsure about performance. I've done about 150km with the big bore kit. I've been gradually going to higher revs but it seems I'm not getting past 8000rpm. It then starts to sputter and has no more power. With the 125 cylinder I could get to arround 10000rpm.
I feel a big difference in mid range power and acceleration. But 100 kph seems to be the top speed. That's less than the 125.

Is this normal during breaking in? Because of the extra friction of the new piston and cylinder?
Or is the carburator too restrictive and should I go for the mikuniVM26 (or bigger?) Or just use a different jet combination?

Any recommendations?
 

Red Ace

New Member
Hi Ruben,

I talked to the guy from world of wheels in Brasschaat.
He said to go for a bigger carb with 150cc kit. 28 (like aps suggested) would be way too big. But a 26mm would be perfect.
He mentioned a 170cc block... i want to know more about that option:)

Grtz

Red Ace
 

DohcBikes

Fuck You.
Racing Ruben said:
Checked the length of the main jets I'm using. They're 8mm keihin jets. At the moment I'm using a 48 pilot, 100 main combination, velocity stack,OORacing header, trumpet muffler with minimal dampening wool, and big bore kit.

A bit unsure about performance. I've done about 150km with the big bore kit. I've been gradually going to higher revs but it seems I'm not getting past 8000rpm. It then starts to sputter and has no more power. With the 125 cylinder I could get to arround 10000rpm.
I feel a big difference in mid range power and acceleration. But 100 kph seems to be the top speed. That's less than the 125.

Is this normal during breaking in? Because of the extra friction of the new piston and cylinder?
Or is the carburator too restrictive and should I go for the mikuniVM26 (or bigger?) Or just use a different jet combination?

Any recommendations?
In addition to sounding rich on the main, a 48 sounds really big for a pilot jet on that engine. Believe it or not a pilot that is too large can contribute to a rich condition throughout the throttle range. Try different jetting first.
 

2b

Been Around the Block
DohcBikes said:
..a 48 sounds really big for a pilot jet on that engine...

In the Ace's standard carb, I think we have all found that the OO Racing 48 (one piece) pilot is spot on. It is what they recommend for Ace engines whether highly modified or standard and they established the size on their dyno. It replaces the three piece pilot that comes standard.

Just posting this again for those that haven't seen them. Database of Ace owner's mods and a piece on jetting the Ace carb that covers the pilot jet.

If any one is considering changing their pilot jet, I suggest you run through steps under the "Tuning After A Pilot Jet Change" heading first to establish whether a change is indeed needed...

https://docs.google.com/spreadsheets/d/1USvziYIyzfyxfZA1YYpQf9eP4djb0GLWbvWcmME88Gk/edit#gid=0
https://docs.google.com/spreadsheets/d/1USvziYIyzfyxfZA1YYpQf9eP4djb0GLWbvWcmME88Gk/edit#gid=1
 

2b

Been Around the Block
Racing Ruben said:
Checked the length of the main jets I'm using. They're 8mm keihin jets. At the moment I'm using a 48 pilot, 100 main combination, velocity stack,OORacing header, trumpet muffler with minimal dampening wool, and big bore kit.

A bit unsure about performance. I've done about 150km with the big bore kit. I've been gradually going to higher revs but it seems I'm not getting past 8000rpm. It then starts to sputter and has no more power. With the 125 cylinder I could get to arround 10000rpm.
I feel a big difference in mid range power and acceleration. But 100 kph seems to be the top speed. That's less than the 125.

Is this normal during breaking in? Because of the extra friction of the new piston and cylinder?
Or is the carburator too restrictive and should I go for the mikuniVM26 (or bigger?) Or just use a different jet combination?

Any recommendations?

Not sure if your symptoms are the same as F3nrich a few pages back on this forum. He found going back to the 125 head was the answer and concluded he got a duff 150 head!

From the spreadsheet about the ace carb it would seem you are running the right main, but may be worth trying one size smaller of the same brand and perhaps even one size larger. What happens when you run through the suggestions in the spreadsheet for sizing the main?



Sent from my iPad using Tapatalk
 

Racing Ruben

Active Member
2b said:
Not sure if your symptoms are the same as F3nrich a few pages back on this forum. He found going back to the 125 head was the answer and concluded he got a duff 150 head!

From the spreadsheet about the ace carb it would seem you are running the right main, but may be worth trying one size smaller of the same brand and perhaps even one size larger. What happens when you run through the suggestions in the spreadsheet for sizing the main?



Sent from my iPad using Tapatalk

I think I solved my problem. After trying different jets (without getting closer to running right), adjusting the fuel screw and some reading on this forum, I decided to put my 125 head back on the cylinder. And just like F3nrich this solved my problem. Now the engine revs smoothly to high rpm. (bonus: no more loud ticking noise )
I wonder if there's something wrong with a few of the big valve heads. Or maybe just a coincidence I ran into the same problems as F3nrich.
Thanks for the advice guys,

Ruben
 

Harrison9757

New Member
Hi guys,

Apologies for digging up an older thread but I'm curious for when you guys have ran the 150 with the 125 head, have you used the base gasket or are you running with just a smear of sealant like crazy? I'm thinking of too much compression with a combination of both.

Thanks in advance,

Sam
 

Racing Ruben

Active Member
Hey Sam,

I didn't use the base gasket only sealant. Since then I've done almost 700km. No complaints yet. Very happy with the 150 big bore with 125 head combination.

Ruben
 

Harrison9757

New Member
Racing Ruben said:
Hey Sam,

I didn't use the base gasket only sealant. Since then I've done almost 700km. No complaints yet. Very happy with the 150 big bore with 125 head combination.

Ruben


Beautiful,

Cheers for that bud.

Sam
 

Erskine

Over 1,000 Posts
Harrison9757 said:
Hi guys,

Apologies for digging up an older thread but I'm curious for when you guys have ran the 150 with the 125 head, have you used the base gasket or are you running with just a smear of sealant like crazy? I'm thinking of too much compression with a combination of both.

Thanks in advance,

Sam

With the 125 head you get more torque and higher compression. This is how they run the Honda TL125 trials bikes with the 150 OHV swapped in.
 

Harrison9757

New Member
Great help chaps!
I've got the 150 but no big valve head atm, was unsure if I needed to wait to get the new head, but now I know this I'm set to go :)

Sam
 

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