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crank shaft question

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From what I can tell the trx crank has a longer pto shaft than the crf? In other words the spline end of the crank sticks out of the case further. Maybe I'm wrong but the 2 cranks I have that seems to be the major difference.

My question is, can I use the trx crank with a crf piston and cylinder? Not worried about the case, more curious about wrist pin sizes and if they are compatiable. I could probably figure this out on my own, but I just wanted to ask to see what answers I get.

Thanks in advance

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Not too worried about weight. What I am doing is making a billet crank case so i can run the motor on my Kart without the transmission setup on a belt drive cyntrifical oil filled clutch on the jackshaft. I am going to run the crank exposed on both sides and put a belt driver pulley on the spline side, and adapt a motoplat ignition on the other side. I think it will work out pretty good, but i think i would want to go with the TRX crank so the splines stick out farther giving me more clearance between the driver and the block. I already have the CRF big bore cylinder and piston, that was why i was wondering if the TRX crank wrist pin is the same.

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The question regading the wrist pin; They're the same.

Im not super familiar with the TRX engine, but I think they changed the bore and stroke from one iteration to the other, so youre going to want to check your deck height so you dont run the piston into the head on accident. Were you going to use the balancer and the oil/water pump assemblies? Im just curious. Id run it dry sump if I were doing something like what your doing. Multi stage External oil pump and all.

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I was going to use an external water pump like the 2 stroke guys use, and i have been giving the oil thing thought. With the Billet OHV kart motors i run, the oil is pushed to the head from the crank case pressure, and I have never had a problem with that system. The Swiss Auto 250 DOHC Kart motors use the same method and suposably thay are proven to work just fine. Not sure of the oil passage on the Swiss Auto engine, and I have been debating on how to get the oil to the head on this 450. The timing chain should cary some but not so sure if that would be enough. With The OHV Motor i run, I have a hose that is connected to the crank case, and goes into the front of the valve cover with a return hole down in the pushrod area, and you can actually see the oil flowing up.

An external oil pump would be awesome. I havent researched anything like that yet, but if you have any info that would be great.

Thanks

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The Honda head is oiled through a passage in the cylinder from the bottom end. The cam chain wouldnt throw anywhere near enough to keep the valve train alive. There is also a squirter in the case to lube the bottom of the piston and the wrist pin too. There isnt any drain back or splash to lubricate that area either. If I were you, now that I think about it, it may be an easier thing to just mill the transmission portion off the Honda cases and weld up and plug the OEM case than to start over. At that point youve got working ignition and cam timing, charging capability if you need it through the aftermarket. The engine and trans oils are separate so dropping the primary drive off and running a belt off the crank. Youre only real issue would be lubricating the balancer and water pump drive. But if you can make a bottom end case, you could make a side case that would get all that done for you too.

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that has crossed my mind also. But i was really into the billet bottom idea. I have a set of TRX cases that i can use. Maybe i can start with that first, and see how it works, and give the billet bottom more thought before attempting it. I appreciate the info, thanks a bunch. I will take any thoughts you can think of.

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