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| XR125 |
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XR125
Renault 5 Driver
Joined: 30 Oct 2006
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| St0rmer66 |
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St0rmer66
World Chat Champion
Joined: 27 Nov 2005
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 Posted: 04:29 - 30 Oct 2006  Post subject: |
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99.99999% sure there is nothing you can do. I've asked this before and have never come across anything on the net. Have tried taking the exhaust silencer off and running it to see if there was some restriction in there but it made no difference. Have tried taking the snorkel bit off the air filter too and it just made it a bit louder (without going faster). I'm sure Honda could have squeezed another 1 or 2bhp out of the engine when they designed it (at the cost of relaibility probably) but you're not going to achieve that with any aftermarket parts.
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:: Honda XR 125 L ('53) => Kawasaki GPZ 500S ('02) => Suzuki SV650S ('00) => Aprilia RSV-R ('51) :: |
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| eddclarke |
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eddclarke
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| XR125 |
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XR125
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| Blau Zedong |
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Blau Zedong
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| Marci |
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Marci
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| Posted: 14:15 - 30 Oct 2006 Post subject: |
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| Quote: | It has same engine as CBR/CG 125 so I guess tuning them is the same. |
CBR and CG engines are completely different... I'll quote a post I made elsewhere on a different site on this issue as everyone seems obsessed with declaring them the same...:
| Quote: | Key difference - valvetrain mass = reduced efficiency. CG has camshaft below the cylinder head, and thus uses lifters and pushrods to help actuate the valves that are in the cylinder head. The CBR has overhead camshaft, and the camshaft opens the valve almost directly by actuating on a rocker arm - it doesn't have the added mass of a pushrod.
While the weight of a pushrod & lifter is seemingly insignificant, when you consider it can account for more than 15% of the valvetrain mass, and it has to open a valve up to 11000 times a minute (or more), it adds up to measurable difference. It's all about inertia - the less weight it has to move, the less energy is required to open the valve, and thus, there is more energy that can be transferred to the crankshaft - meaning more HP to the wheels. So even if BOTH were tuned/modified to produce the same compression ratio, the CBR engine would still beat the CG engine if mounted in the same frame.
CBR is a true 125cc capacity. CG is a 124.1 capacity. Cooling and gearbox aren't really performance differences. Air vs Water doesn't mean one engine goes faster than another. Just that one is DESIGNED to go faster than another and requires uprated cooling. Gearbox - can ratio the CBR with a 5speed box to match a CBR with 6speed box and both will more or less sit head to head in a 1/2mile drag. 6speed box will win by a VERY narrow margin based on a slightly longer amount of time in the torquey revrange than the 5speed.
Simplest way to put it is that rev per rev, engine vs engine (ignoring other consequentials such as aerodynamics and dry weight) the CBR makes more HP and more torque than the CG, mainly due to the cam arrangement. The other factors (aero and weight) simply work in the CBR's favor to increase it's performance lead over the CG when packaged as a "bike" rather than just looking at the engine. |
Aftermarket pipe, remove airfilter completely, rejet on a dyno. S'as good as it gets for cheap and easy. Other than that it's bore & skim, lighten flywheel, port n' polish, lose as much weight off the wheels as possible. It'll cost £1000ish to have enough work done to make any major difference to the final speed. We've been racing using the CBR engine for the past 2 years and have tried more or less every trick in the book other than handing over large lumps of cash - all make naff all difference.
If you have a 4 stroke 125, then as it comes is as good as it gets unless you're loaded or have your own machineshop and the necessary experience.
| Quote: | I've seen a vid on youtube of a dude getting 90mph out of his cbr125 |
If it's the vid that I think it is it's a wolf in sheeps clothing - CBR150 (which has a 4 valve head) with CBR125 bodywork. The dyno tests shown are inaccurate as no wind resistance applied, and the dyno figures displayed in pic in thread were done in 1987, before the CBR existed (date and time is shown on the dyno paperwork).
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FAB-Racing MiniMotoSidecars - Back with a vengeance - F1 Class 2011...
CBR170 engine, custom chassis - www.minimotoscene.co.uk |
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Old Thread Alert!
The last post was made 19 years, 163 days ago. Instead of replying here, would creating a new thread be more useful? |
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