Porting!

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How do you find throttle response from snapping it open?

Looks like you have opened it up alot, maybe a touch too much?

Also did you polish your intake port?
 
instant throttle response. it is a 187cc after all....


I didnt open the entire port up as much... im using a TM33 so i opened up the manifold and then just tapered it down from there, i only finished it with a 200 grit sand paper roll, nothing over the top as im against polishing the intake to mirror finish tbh.

i also opened up the exhaust a fair bit, but ill keep that one to my self :)
 
thought so, looked like you might of polished the intake, which isnt the best when the fuel starts seperating out of the air.
 
have a look for my helmet cam footage in the videos section and you can listen to the throttle response :O
 
What do you think?



Intake is finished with 400water sanding paper. Exhaust with 250. The difference really feels! I also fitted a Keihin PWK 28mm. The motor is Lifan 140cc. Further tweaks to come!

Post pictures of your own heads ppl!
 
Did you think about building the port floor up? Did you think about the effects to your valves from grinding out your valve guides, especially the exhaust, And polishing your intake port decreases the power output. other than that very nice.
 
I'm aware of that all. I didn't actually make the ports a lot bigger, i just smoothed the floor and rised the roof. The floor should have been built up with chemical metal but i was too lazy:p .
The ports of my 150cc road-legal bike look just the same, guides ground off, and no problem after 5000km.

I may have smoothed the intake a bit too much, yes.. It just looks good like that:D . It is still far from a mirror finish.
 
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thank you for photo very good. more please, i lifan head cylinder 27mm and 23mm. how big more install please ask.
 
kesman20 said:
thank you for photo very good. more please, i lifan head cylinder 27mm and 23mm. how big more install please ask.
Click to expand...

This thread on Planet Minis shows a new big valve head (similar to a Lifan BVH) with 30 intake and 23.5 exhaust valves plus a bigger inlet manifold ...

new import race head - Planet Minis

In a nutshell , to maintain high intake air velocity , you put back onto the port floor what you take off the roof ... ie retain the stock port volume whilst straightening up the flow path ... That way you gain top end power without losing bottom end power and throttle response ...

This Wikipedia link has a good diagram showing the best ways to port heads ...

Cylinder head porting - Wikipedia, the free encyclopedia
 
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Yeah I forgot to add "unless the port is too small in the first place" ... For on and off the throttle dirt racing including sliding corners , wheelstanding , lugging taller gears etc you want all the snap and pull you can get ... You can't be in the right gear to match the revs at all times ... The best way to work out what works is to port a head gradually in stages and time the bike over a measured distance each time to see if you're genuinely improving performance or not ...
 
I work so the cylinder head. ok?
p1030653zh1.jpg
 
i think those groves are to help direct air flow. i've seen it done in engine blocks and its meant to work well when done correctly. i could be wrong though
 
Mack said:
Yep, the two springs are stock. I'll warn you now, the only major drama doin this without a spring compressor is gettin those little barstard retainers back in. It needs great patience or save yourself the drama and when your ready go to any bike shop and get them to pop them in. Its 2 mins with a compressor.

Yes the ports have a bit of machining from the factory at the opening. The ducars I have seen have been opened out wide in this spot but then use a way undersized gasket and block the flow.
Click to expand...

simple compressor...find a nice g clamp and have a look at a real compressor and then! look at your angle grinder...itll make sense:) worked on my old postie a treat
keep that intake roughly finished while your there...

i also have tried an alloy gasket(go the bundy rum!!!!!!) but intentionally made the hole too small...trim this dag into vanes, that get the air to spiral as it flows through... tricky part is...which way to twist them?
 
sumppa said:
I'm aware of that all. I didn't actually make the ports a lot bigger, i just smoothed the floor and rised the roof. The floor should have been built up with chemical metal but i was too lazy:p .
The ports of my 150cc road-legal bike look just the same, guides ground off, and no problem after 5000km.

I may have smoothed the intake a bit too much, yes.. It just looks good like that:D . It is still far from a mirror finish.
Click to expand...

ive tried really hard to have a look inside my intake while actually running the engine, and for some reason, i cant do it:p ie, who cares what it looks like when its bolted together? its how it improves performance that counts...
 
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