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Discussion Starter · #21 ·
Did you measure the diameter of the intake port on the head? It doesn't do any good and probably will do harm if the carb is bigger than the intake port. IIRC, the intake port on the TW head is about 30mm.
Yes, the intake manifold/boot is even smaller. but I thought since XT225 uses 34mm carb, the same size should work. XTNG later replied even though their carb states "34", in real the venturi is 32mm.
I'd imagine the intake port on head could be atleast drafted/smoothened to get rid of the sharp edge. I am not saying I will use the honda manifold, rather that it is a possibility. I plan to document as much numbers as I can - even go as far as to calculate real world horsepower curve by knowing weight and acceleration. so we will see. the friend I was mentioning here and there is going little bit different path. he's going to swap only crank and whole top end, doesn't plan any modifications, so his will be a stock 225 with TW's MV28 carb. only thing not stock is his pod air filter, since his TW is quite custom. I will be comparing his and mine.
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The only way to get the true wider ratio in the dub is to use Placerlodes shaft extension because 1st gear is part of the counter shaft.
really? then how is this possible?
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What you have identified below (in pink) is not a gear, but is a splined section of the output shaft that the transmission gears slide on. Except for length "A", this section is identical for both the TW and the XT/TTR.

View attachment 220355
Looks like a larger diameter.
Is it the wheel shaft then that has the gear as part of the shaft?
 

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Discussion Starter · #26 ·
Looks like a larger diameter.
Is it the wheel shaft then that has the gear as part of the shaft?
It looks bigger because it is at different angle and you see the edge of the splines.
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here you can see the shaft that has gear already on it (1 in pic) It's the main shaft, the one connected to clutch. The gear on shaft is 1st gear - this is true for both 6spd and 5spd. I'd say it's manufactured that way, because of the torque that 1st provides.
For a while I was worried I missed something when researching. :D
 

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It looks bigger because it is at different angle and you see the edge of the splines. View attachment 220357
here you can see the shaft that has gear already on it (1 in pic) It's the main shaft, the one connected to clutch. The gear on shaft is 1st gear - this is true for both 6spd and 5spd. I'd say it's manufactured that way, because of the torque that 1st provides.
For a while I was worried I missed something when researching. :D
Thank you for clearing that up. I had the shafts backwards in my head then.
The gear is fixed on wheel shaft.
Can anyone explain why the shaft that the sprocket goes on is called the countershaft and the other one is called the wheel shaft and not vice versa? ihni.
 

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Discussion Starter · #28 ·
Thank you for clearing that up. I had the shafts backwards in my head then.
The gear is fixed on wheel shaft.
Can anyone explain why the shaft that the sprocket goes on is called the countershaft and the other one is called the wheel shaft and not vice versa? ihni.
to be real, I too wondered that :D for me, a better name for this shaft would be output shaft or sprocket shaft.
I looked at parts diagram and there it is called drive axle, which makes sense too.
Is that a TW200 forum thing, or is "countershaft" used elsewhere?
 

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Great thread!
I plan to do a 225 conversion down the road when my Dub starts showing evidence of wear - at just under 16,000mi it seems brand new. I do change the synthetic every 1000mi religiously (often a little before). Interested in the milage I get out of my favorite toy keeping everything internally as slippery as possible. With only a quart for a change ...why not?
 

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Some brands refer to it as "drive" and "driven" just as they do the two sets of gears. One thing I've learned from owning a repair shop that serves multiple brands is that there's no such thing as standardized terminology in the motorcycle industry!

Even digging through the parts fiche can be a real pain because what Suzuki would call a "choke cable" would be called a "starter cable" by Yamaha (or is it Kawasaki that uses that odd terminology?) Anyway, it does indeed get confusing at times.
 

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Discussion Starter · #32 ·
Cylinder set arrived! let's see how it looks together with the head. and weight of the piston.
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I measured the ports: IN 29mm / EX:30,4mm
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In my very new to porting eye I would say these ports aren't as bad. I'd say the ports are different than on genuine yamaha head, does anyone have pics? I'll try to dig some pics on the net.
 

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You mentioned that you weren't sure the timing lobes on the YFM250 head was same as the XT225/TTR225 head. I also am wondering about the head volume as it pertains to compression ratio. Any info on that? Now that you have the parts, you could measure the volume of area for TDC and BDC to get the true ratio.

My TTR225 motor with the 229cm3 cylinder and piston kit is still smoking when warming up from cold. I was hoping that was due to an overfilled crankcase, but it doesn't seem so now that that's been resolved. I now think it would be valve guides since compression is so strong on this motor. If I pull the head, it might be easier to just get the head you bought and slap it on. But I want to know about volume and compression ratio before doing anything like that.
 

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Discussion Starter · #34 ·
You mentioned that you weren't sure the timing lobes on the YFM250 head was same as the XT225/TTR225 head. I also am wondering about the head volume as it pertains to compression ratio. Any info on that? Now that you have the parts, you could measure the volume of area for TDC and BDC to get the true ratio.

My TTR225 motor with the 229cm3 cylinder and piston kit is still smoking when warming up from cold. I was hoping that was due to an overfilled crankcase, but it doesn't seem so now that that's been resolved. I now think it would be valve guides since compression is so strong on this motor. If I pull the head, it might be easier to just get the head you bought and slap it on. But I want to know about volume and compression ratio before doing anything like that.
I would guess the head volume is the same since we can see difference in pistons, but I plan to measure head volume, just don't know when I'll get to that.
I want to get the cam out and measure it too
 

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Discussion Starter · #35 ·
I would guess the head volume is the same since we can see difference in pistons, but I plan to measure head volume, just don't know when I'll get to that.
I want to get the cam out and measure it too
Last thing I need is precise enough syringe. I took the camshaft out, measured cam lift, took a photo and measured timing in Fusion360.
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Both intake and exhaust cam lobes are as Service Manual specs - 36,6mm - these specs are the same for TW125/TW200/XT/TTR225/230 and YFM250
parameter you won't find in manual is timing of the lobes - as measured by me 123,3° in cam degrees.
I want to do this once again and find where is TDC in relation to cam lobes.
If I get all the things needes, I would like to measure actual valve lift, once everything is completed.
I've read on webcam website, that the smaller the angle I measured the more power at low to mid range and vice versa.

I am thinking of making a thread called TW225/6spd bible, where we put all the info?
 

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Instead of syringe, what about volume by weight? Weigh with a liquid of a known specific gravity. Distilled water should be 1.00 sg, right?
1cc of water at 3.98c (the temperature water achieves maximum density) is 1 gram.
 

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I wish I'd found the head you ordered before I bought mine. I ended up with a used TTR head that had a bad valve, then ordered all new valves, springs, keepers, etc. Your option would have been way cheaper and easier.
 
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Discussion Starter · #38 ·
Instead of syringe, what about volume by weight? Weigh with a liquid of a known specific gravity. Distilled water should be 1.00 sg, right?
1cc of water at 3.98c (the temperature water achieves maximum density) is 1 gram.
I thought of that too, however I don't know if I trust the scale at weighing accurately aroung 24g of water when the whole 3kg head is on it. I may try both approaches and compare them.
 

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Don't neglect to measure the volume of the dome of the piston and the valve reliefs otherwise your calculations will be meaningless -- I am assuming you will be calculating the compression ratio.
 

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Don't neglect to measure the volume of the dome of the piston and the valve reliefs otherwise your calculations will be meaningless -- I am assuming you will be calculating the compression ratio.
I've always used the engine compression divided by the atmospheric air pressure. I have a weather station that measures local pressure, then I 'calibrate' it to the local airport about 5 miles away and same elevation.
For example; my compression was 145psi. Sealevel pressure is 14.7 on average so tht would calc to 9.86:1 or round to 9.9:1
But on the day I tested here at my house at 1930' above sea level, the pressure was 13.7. Pressure usually will drop .5 per 1,000'. So using the formula again, 145 divided by 13.7 I was actually seeing 10.58:1 compression ratio. Round off to 10.6:1. That's getting up there! And while I don't have a lot of experience working on 4-strokes, I do have some riding them. This bike has the most compression braking I've ever encountered, especially on throttle chops on downhill it's quite noticeable. In fact, I thought the rear brake was dragging and checked it to be sure it wasn't.
How accurate my measurement is, I don't know. But it is something I can repeat for comparison. I'd guess I check my compression about once a year or so. Many times at oil changes where I want to warm up the oil good before draining and I'm home where the compression gauge is handy and the garage to work in. Only takes a few minutes. I also get to inspect the spark plug and use my endoscope with light to look down the plug hole.
(here's a link to the endoscope I have. No longer available but when I bought it in 2015, it cost me $21. Cheap and works on all sorts of things. Down sink drains, in your ear, well, you use your imagination....

My buddy has one that bluetooth connects to his phone so that's pretty handy too. No need to cart a laptop out to the garage.
 
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