TRX250R.ORG
Workshop => Engine and Bottom End => Topic started by: rablack21 on August 19, 2014, 04:38:53 PM
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My setup:
88 TRX set up for MX
ESR 310 pv
38mm cast Smart Carb
ESR TRX 5 pipe and silencer
Vforce 3 reed cage
CR 250 ignition
I am doing some testing on my race quad to see if the flywheel weight is helpful or hurtful. I thought I would share this information with anyone who might also be interested. I bought and installed a Steahly flywheel weight 10 oz. So far, I have only taken it down the road and around my subdivision, but was able to pull a couple of full stretch runs on it. So far, I have not noticed a great deal. The engine still revs up pretty quick. It might be just a tad slower on revving up when going through the gears, but if it is, it is not by much. So far this is all I have noticed. I've only ridden offroad once and it wasn't in any area that I could tell much. It does seem to keep it centrifugal momentum up a little better and doesn't slow down the revs as fast. The real test will be when I get it to the track and see how traction is affected and how cornering is affected. Right now, I am running 14/38 gearing. I'm gonna run it on the track with what I have on first and see how it does. Then I will probably switch to 14/37 and see how it likes that. These are just a couple initial impressions that I have of the flywheel weights. As of the moment, I can't tell you whether there is a benefit to running the weight or not. I hope to go to the track Friday and do some tested. Stay tuned!
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Thanks for the report. I haven't got around to buying one for mine yet. Keep us updated.
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Be cool if you could run a couple laps without it come in put the weight on and run a couple more and compare lap times
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My setup:
88 TRX set up for MX
ESR 310 pv
38mm cast Smart Carb
ESR TRX 5 pipe and silencer
Vforce 3 reed cage
CR 250 ignition
I am doing some testing on my race quad to see if the flywheel weight is helpful or hurtful. I thought I would share this information with anyone who might also be interested. I bought and installed a Steahly flywheel weight 10 oz. So far, I have only taken it down the road and around my subdivision, but was able to pull a couple of full stretch runs on it. So far, I have not noticed a great deal. The engine still revs up pretty quick. It might be just a tad slower on revving up when going through the gears, but if it is, it is not by much. So far this is all I have noticed. I've only ridden offroad once and it wasn't in any area that I could tell much. It does seem to keep it centrifugal momentum up a little better and doesn't slow down the revs as fast. The real test will be when I get it to the track and see how traction is affected and how cornering is affected. Right now, I am running 14/38 gearing. I'm gonna run it on the track with what I have on first and see how it does. Then I will probably switch to 14/37 and see how it likes that. These are just a couple initial impressions that I have of the flywheel weights. As of the moment, I can't tell you whether there is a benefit to running the weight or not. I hope to go to the track Friday and do some tested. Stay tuned!
10 oz is not much weight if the weight is a disk and will not change the moment of the crankshaft very much. 10 oz added to the outside circumference of the flywheel would make a noticeable difference. The majority of the kits that add weight to the flywheel have a constant thickness disk whose center of mass is located at a much smaller radius than where the outside of the fly is located.
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Flywheel weight would be rather pointless if the weight wasn't added to the outside circumference of the flywheel. Both Steahly and MSR flywheel weights are set up on a larger radius. Compared to the weight of the cr 250 flywheel and the trx 250r flywheel, a 10 ounce change ( 283.49 grams) is quite significant.
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I think the 16oz made a noticable positive differance in idle quality and honestly for the guys that want the somewhat stock feel that is the weight to go with.
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Update:
So I tried my weight this weekend at a mx race. I honestly can't say that I noticed much difference to not having it. It's hard to say with only two motos of opportunity. I will say that it may have played a role at the starting gate. It was a loose sandy track and the starting gate was such as well. I figured that I would get alot of wheel spin off the line, but that was not the case. I was launching in 2nd gear, throttle at 3/4, dumping the clutch at take off, weight leaned forward over the gas tank. On the first gate drop, I come out of the gate wheels high. I had to let of the gas, quickly clutch it, and then take off again. On the 2nd gate drop I made sure I was far enough forward; with my crotch basically up to the gas cap with my head leaning over the handlebars. Same take off procedure as before. Again, on the gate drop, I come out of the gate doing a huge wheelie having to clutch it and go again. I can't say with all certainty that my ridiculous amount of traction was due to this flywheel weight, but it is possible.
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Good report... I'm also looking into one of these for my build.....
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I run a flywheel weight on both my MX and XC CR250 Ignitions. It made a noticeable difference for me. I was never happy with the CR ignition untill having the weight added.
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I run a flywheel weight on both my MX and XC CR250 Ignitions. It made a noticeable difference for me. I was never happy with the CR ignition untill having the weight added.
Kyle, What was it that you noticed about it? I'm curious. Again, I have only gotten to run this for a short bit on the track, so I am still keeping my ear to the ground, so to speak, to see if I notice anything different from before. What amount of weight are you running?
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15 ounce weight. IT has more bottom end coming out the of the corners. Or should i say more resistance to stall. I can drive a corner harder, slide the rear end and roll on the throttle with less likeliness to bog. It also smooths out the power.
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Hmm. Maybe I just don't have enough weight to see quite as much difference.
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I think the 16oz made a noticable positive differance in idle quality and honestly for the guys that want the somewhat stock feel that is the weight to go with.
15 ounce weight. IT has more bottom end coming out the of the corners. Or should i say more resistance to stall. I can drive a corner harder, slide the rear end and roll on the throttle with less likeliness to bog. It also smooths out the power.
Where did you guys find a 15oz or 16oz flywheel weight? What brand are you running? The biggest size that I have found so far for a cr250 is 14oz.
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You wont like where I get them at. They make them in house.
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You wont like where I get them at. They make them in house.
I understand. Thank you for replying back anyway. How did you decide what weight to go with or did you just experiment with several different weights?
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It was the most weight we could fit on the end of the flywheel. Total CR flywheel and weight is right at 800 grams total. The CR flywheel by itself is less than 400 grams. The OEM TRX flywheel is 1100 grams.
Now this is straight weight. The CR flywheel is much smaller diameter, my flywheel weight is larger diameter which helps, but the TRX OEM is not only heavier, but much larger diameter giving it more rotational inertia. I could run throught the calcs, but the point is that the Stock ignition still has a lot more.
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It was the most weight we could fit on the end of the flywheel. Total CR flywheel and weight is right at 800 grams total. The CR flywheel by itself is less than 400 grams. The OEM TRX flywheel is 1100 grams.
Now this is straight weight. The CR flywheel is much smaller diameter, my flywheel weight is larger diameter which helps, but the TRX OEM is not only heavier, but much larger diameter giving it more rotational inertia. I could run throught the calcs, but the point is that the Stock ignition still has a lot more.
Thanks for this info Kyle. I was gonna weigh these components myself for reference, but now I don't have to. With me having only added 283 grams with this 10 oz weight, it's probably not enough to quite see the difference that I am looking for. I might bump up to a 14oz-16oz and do some more testing. Sounds like you like the additional weight pretty well.