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594 Posts
Discussion Starter #1 (Edited)
This is for the guys who wants a more crisper lively output from the TW, for me it made a HUGE difference in performance when it comes to acceleration and low end grunt, I'll say its about a 20% improvement in performance for me.

I did a lot of research with all the available options when I decided that it is time replace my carburettor and I decided to try out the Keihin carb that comes out standard on all Honda and Chinese bikes, also included is a built-in acceleration pump which gives the bike extra power when accelerating

The fact that this project will only cost you around $ US 70 makes this a win-win situation

The experiment was a huge success so this is the write-up for installation. Go to for the original post.

You need to have patience for this project, this is a bit tricky and I covered all of the things that you need to do for this modification, if you have any questions feel free to pm me

First I'm going to run through the things that you need to buy for this project

Go to and type "Keihin pz30 Carburetor + Twister + Cable" into the search box or Click Here

Choose a package in the result that has the carburetor, throttle cable and twist grip included, go ahead and order it

then you have to order the intake manifold

type the words "Carburetor Rubber Adapter Keihin pz30" and the order it

this is the right one that you must order


then you have to order the starter/ kill switch, type the words "Off-road motorcycle electric starter"

then you're going to have to wait anything between 2 weeks and 2 months for the spares to arrive, depending on whether you used the courier option or the send via postal service option


Remove the seat and the fuel tank

Remove the old carb and the old throttle twister with the old cable

this is where the fun begins . . . . . .

you're going to have to trim down the two rubber boots and then glue them to each other

in the end, the two of them attached to each other must be about 1 1/2 inches (38 millimeters) long

be careful when sawing the old manifold because a replacement one will set you back $ 50

after sawing the rubber boots take them one at a time, put them on a piece of sand paper and sand them until the surfaces are even

this is how the two rubber boots look like afterwards

now we are going over to the other rubber boot, you're going to have to cut away the REAR boot so that when you put the carb against the rear boot when it is in position on the air box there will be a 1 1/2 inch gap in the FRONT between the carb and the engine so that you can fit the other two rubber boots also

now you're going to have to take the carb and hang it from the frame of the bike , I did it with isolation tape

the next step is to take duct tape and a tie-down, wrap the duct tape carefully around the carb inlet and boot outlet so that you have an airtight seal, this is the most straightforward and practical solution for me

buy a plumbing clamp and cut an aluminum sheet (I'm sure you can use an old tin can also) and get it ready to put it around the rubber boots

get yourself a tube of Loctite SI 5699 or something similar that is capable of sealing AND to withstand high heat temperature

apply the sealant all around the rubber boots on both sides and then also on the inside of the aluminum sheet

put the clamp wit the aluminum sheet on the inside around the rubber boots and tighten the clamp until there is a seal, not too tightly otherwise you're going to separate the rubber boots from each other

wait for at least 5 hours or preferably overenight for the silicone to harden properly so that there is an airtight seal and you will have a solid, reliable boot!

all that is left to do is to route the throttle cable and to attach the new throttle twister to the handle bar and you're ready to go

the finished product


594 Posts
Discussion Starter #4 (Edited)
Thank you brother Tom and buellzebub

buellzebub - yes I have a stock 200 engine and the carb is suitable for any 4 stroke engine between 200 - 250 cc, just go to if you want to find out more about the carb, type Keihin PZ30 in the search box

19,561 Posts
Might a rubber no-hub, or hubbed rubber coupler join the manifolds?
American plumbing suppliers have these for joining a variety of pipe diameters. They are quite strong and secure.
What is the approximate outer diameters of the two manifold sections to be joined?

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594 Posts
Discussion Starter #9 (Edited)
Yes Fred, I'm sure it can work, just as long as it is a high quality rubber that can withstand very high heat, especially when you go trail riding on a hot summers day, temps go all the way into the red.

The Loctite gasket maker silicone is a superior product which I tried and tested on my bike during the last couple of months and believe me, that manifold is as solid as you can get, I don't have to worry about air leaks at all no matter how high the temps go

Is is also nearly impossible to align the two manifolds perfectly with each other, no matter how hard I tried, there is always a small angle between them, that's why I prefer to use silicone sealant also

594 Posts
Discussion Starter #10
Great job and a great write up. How is the top speed now? How is your butt dyno performance figures?
The butt dyno performance figures are simply out of this world bro, as soon as I have the money I want to put the bike on a real dyno to have a look at the graph

I want to go for the first high speed test run today and will report back afterwards:p

594 Posts
Discussion Starter #12
I went for the first proper 100 mile shake-down run today and there was no hiccups at all.

The carb excels with acceleration and bottom end grunt and then there is also that wonderful crisp throttle response . .

At the top end it behaves very much the same as the stock carb, although it feels like I can maintain my cruising speed better going uphill.

At the moment my guess is that the fuel consumption is the same as the stock carb also

This looks like it might be too good to be true but this is my honest ride report, one of the ways that I experience the difference is when I return home from work every day -

I live on top of a small hill, in the past I always had to go around the last corner, gear down to 2nd gear and twist the throttle to maintain momentum going up the last 100 yards.
Not anymore, now I simply stay in 3rd gear and slightly open the throttle to get to my destination . . ;)

19,561 Posts
Great report on your success.
Imagine the extra petrol purchased will be a bargain compared to the extra whoopee generated as you inject that extra petrol in one squirt at a time. Would imagine top speed should remain limited by un-modified engine鈥檚 inability to ingest and pump out much more air irregardless of fuel added. From an abstract viewpoint all internal combustion engines are essentially air pumps.
What鈥檚 next, bigger valves? :p

594 Posts
Discussion Starter #14
Bro, I'm burning half a pint of oil per month at the moment so if I get the time I'm going to have to replace the rings hopefully before the end of the year, maybe a 70 mm piston, carefully polish, hone and grind the needed things inside the engine but nothing beyond that for now, the gearbox is still in a good condition though.

I'll keep you guys updated with the progress:p

594 Posts
Discussion Starter #20
How to Fix the Choke

It's been a week since I installed the carb and my bike is a sheer pleasure to ride, it is summer time over here and I don't even need the choke to start the bike in the mornings.

I just had to do a small but important fix to the carb today, the carb comes with a bracket which I can use to install a choke cable to the carb but since the carb already has a choke lever it is much easier to just use the lever.

All I had to do is to remove the bracket

and then I had to attach this metal plate in place of the bracket

this is the choke position when it is not in use

this is the choke position when it is halfway open

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