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  1. #1 Need gearbox ratio information 
    C-Moto Not-so-Noob
    Join Date
    May 2017
    Location
    UK
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    11
    OK so this gets complicated.

    Here are some things I have discovered recently while tearing apart the 125, 150 and 250 twin engines and making engines for my bike.

    The engines I've been using are 244FMI (Jinlun 125), DD247E (Regal Raptor), and 253FMM (Quadzilla quadbike engine).

    I've already made an interesting engine by putting a shortened 253 top end on a 244 bottom end and it ran very well.

    The 244FMI crank can be taken apart at a machine shop and turned around to make a 360 degree crank, which I prefer as it means I can use a single carb for simplicity. The head is also interchangeable between the engines, but the 244 has 18mm inlets and the 253 has 22mm inlets. This may or may not make much difference in real terms. The 253 cam fits any of these heads.

    The 247 (150cc) head I have also has 22mm inlets, so you can put a 150 head on a 250 engine and that raises the compression but keeps the bigger inlet size.

    I've discovered that CG200 six spring, widened clutch insides will fit in both the 244 and the 253 engines, giving a nice strong six plate clutch.

    I have made an adapter to use both the 244 and the 253 clutch baskets which are exactly the same size but only differ in the center bit, but my adapter means I can use any of these now.

    I discovered that the valves and valve springs are identical in both engines. However, the 244 (125cc) uses a shorter cam chain than the 253 (250cc) because it's altogether about 15mm shorter. You need to use the correct rocker cover on whichever head you use because the 253 has a bigger head even though the bolt pattern is the same.

    I discovered the engine cases themselves are also identical between the two engines so in effect you can put any internals into any engine cases between the 244 and the 253 as long as you remember to use the short barrels with the short crank.

    Now I've been taking gearboxes apart because I was attempting to make a different gearing by using parts from the 244 and the 253 gearboxes mixed together. So far I have discovered some slight differences but some parts do interchange so now I am looking for information about the gear ratios of the individual gears so I can decide what to use.

    Other than certain bearings and clutch differences there's not that much difference between them so I should be able to make a hybrid gearbox, but I can't find any information about the actual gear ratios of each gear for the 244 and 253 engines.

    Any information?
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  2. #2 Re: Need gearbox ratio information 
    Senior C-Moto Guru humanbeing's Avatar
    Join Date
    Dec 2008
    Posts
    1,475
    Most chinese are lazy ass... The ancestor <CB125T /CA250 (Rebel) https://www.impex-jp.com/catalogs/moto/honda.html CM125 https://www.bike-parts-honda.com/hon.../Engine/1/3868 > are good enough as wild guess material
    http://www.regal-raptor.com/en/pdf.a...sersManual.pdf listed some gearbox ratio used by Regal Raptor
    Last edited by humanbeing; 07-05-2018 at 01:13 AM.
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  3. #3 Re: Need gearbox ratio information 
    C-Moto Not-so-Noob
    Join Date
    May 2017
    Location
    UK
    Posts
    11
    OK, that's some useful information but not sure which Honda gearboxes the Chinese engines copy. Probably the 244FMI are copies of CBT125, and the 253FMM are probably copies of Rebel engines. As far as I can tell from my experiences the 244FMI and the Regal Raptor 125/150 use the same gearboxes.

    What I'm trying to do is build a gearbox with a lower 5th gear. On my bike the low gears of the 253 gearbox are annoyingly low when you get the gearing right for 5th gear highway speeds. I'm currently using a 16" rear wheel with a 110/90 tyre and an 18T front sprocket. Using about a 27 or 28 rear sprocket seems close to the right gearing for last gear but I prefer a higher geared first and second so I'm just seeing if I can create a different gearbox to suit my wants.

    Alternatively I could maybe run a dual sprocket on the back, one for low geared trailer pulling work and one for higher geared normal use where I could quickly change the chain over from one to the other depending on what I need without having to put the bike on the center stand and pull the whole axle out and change sprockets.
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