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Addy1982

Sr 125 - More power!!!

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I realise this has been covered in the past but to avoid having to go through a load of old threads, I thought I'd start a new one.

Ok, my question is this... Can any more power be gained from this little engine? I'm not looking for loads of extra top speed, but merely a little more power to be able to hold the speed a bit easier when faced with wind or hills.

Anyone's personal experience with air filters or different carbs etc would be greatly appreciated.

Please avoid the sarcastic remarks like - "yeah more power can be gained by passing your test and buying a bigger bike - hahahahah" I'm well aware of this, I just want to improve my wee bike as I'm quite fond of her.

Thanks guys.

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Ok, so I never modded my YBR as I knew I would eventually get my full licence and a bigger bike... But aside from that I genuinely found that Essos' premium fuel worked wonders.

Not sure how it would work for your SR as mine was a 2012 plate. In addition to that I understand there are sceptics out there with regards to fuel. But I did genuinely noticed a difference. I live in quite a hilly place and once I switched from Tesco standard to Esso premium I found I needed to downshift less on hills I was used to riding.

Perhaps worth a try as something that wouldn't effect your insurance? Just appreciate that you'll need a couple of complete tank fills to remove the previous fuel.

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Hi addy " small 4 strokes need a lot of engineering for a power spike, your on ,12bhp.. a 2 stroke is easy to get power gains,

DTr 125 is 16 bhp. but can produce about 30bhp, [ yz125] same cc"s but with porting , 34mm carb , and expansion pipe,

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Try this:

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When I changed my front sprocket I found each gear was 'longer', so although initial pick up was slow, I am getting more mph on each gear. I do find I can't stay in 5th so much uphill, but she is happy pulling uphill in 4th at 50-60. Not that I recommend 60 in 4th for long periods of course!

You could change the sprocket down to 13 teeth, which would give greater acceleration through the gears, but top end would be compromised.

As Blackhat says there are only 12 horses available and there is no power valve on a 4-banger, so not a great deal else could be done. I don't think changing the exhaust/ air filter is likely to make any real difference to power that you would notice and the engine does not have enough power to think about a turbo.

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Hmm, so maybe the fuel is the first thing to try. I was thinking of a smaller front sprocket for better acceleration through the gears. It would mean I was revving slightly higher when i get to fifth gear, which I would hope might keep my speed up.

Are there not 4-stroke 125s with 15 hp on the market? Why is it that the sr can only manage 12?

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4stroke hp comes from the cylinder head.

Cam, airflow, valve sizes, squish. But and its a biggy.

All your power will just come from somewhere else. More top end will destroy the bikes torque. A 125 hasnt got much spare to begin with. Esp as a single. The twins were much better but were sidelined by the newer restrictions.

People are not giving you grief when they suggest a bigger bike. Its a genuine sentiment. That little 125 is great for learning and shoestring budget transport.

If you work within its limits it can ride with the bigger stuff to. If you mates are genuine. Ask andrewelvisfan. He rode with a 250 and a 650 to Squires from Cambridge on L plates.

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As nice as it would be to see a speedo do the same as it does in my car, if the journey is on the right roads with the right scenery I enjoy just being out on the bike. There are plenty of back roads where I live with twists and turns enough to be interesting. Like cynic says if you are with genuine friends and bikers, riding with bigger bikes isn't a major issue.

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If I had the space and money I wouldn't hesitate to buy another small CC bike. Had such fantastic fun on my YBR. As Andrew says, with the right roads it doesn't matter what you're on!

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The point being, aside from a sprocket change there isnt any more.

4strokes are not restricted. The engine is designed to do what it does.

Even the latter 2 stroke 125's are weak pretenders to the monsters around in the 90s.

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Sod it, doing my test and buying a 'real' bike! After 97 miles, I have only achieved 59 miles per gallon. Not worth it when I can barely scrape 60mph. So much for the cheap commute. I can get 50 miles per gallon with the car doing that speed!!

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If you had a new 125 it would be more like 100mpg.

Dont forget in your costs. Insurance, tax as well as purchace and consumable costs are far less than the car. Not to mention parking and skipping traffic ques.

Bear in mind some bikes do far less. Ridden hard my 250 will drop down to mid twenties. My old 600 dropped to sub 20mpg on the TT course on the IOM. Was fun though.

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Suppose if your main motivation for riding a bike is cheaper commuter costs then as Cynic says a newer 125 might be the way to go. Great selection these days with fantastic low running costs.

Although if your motivation is the desire to ride bikes for pleasure then you'll find the lower mpg tends not to come into play. Getting a bigger bike has its own associated costs as Cynic says - lessons, test etc so make your decision based on your own motivation.

Let us know what you decide!

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