Reservoir-dog Posted April 30, 2010 Share Posted April 30, 2010 Hi There I've just bought a 2004 6k miles xvs 125. I've only done 53 miles all through London traffic and I always avoid to use first gear because I feel it much to short to use in traffic. I am considering changing the front sprocket making it bigger. Maybe just one tooth but I was told that just one tooth will not make to much difference. Any feedback on this? Link to comment Share on other sites More sharing options...
Paulwhite Posted April 30, 2010 Share Posted April 30, 2010 ul have trouble trying to find somewhere that will do the front sprocket with 1 tooth less (or 1 tooth more) ul b better off getting a rear sprocket done just 1 tooth extra/less wont do allot ul be better off getting 3 to 5 teeth put on/off (hence why its better doing the rear sprocket) just incase u didnt know if you opt for more mph ul loose out on torque which will slow down ur acceleration and ul struggle to get up hills (just something to consider) at the end of the day 1st gear on a xvs 125 is just for pulling off (because its a heavy bike for a 125) where as on a bigger bike you can cruise through traffic quite happily in 1st. Link to comment Share on other sites More sharing options...
oldtimer Posted April 30, 2010 Share Posted April 30, 2010 ul have trouble trying to find somewhere that will do the front sprocket with 1 tooth less (or 1 tooth more) ul b better off getting a rear sprocket done just 1 tooth extra/less wont do allot ul be better off getting 3 to 5 teeth put on/off (hence why its better doing the rear sprocket) rubbish there are plenty of companys out there that do them.try this link reservoir dog http://www.wemoto.com/bikes/Yamaha/XVS_125_Dragstar/00-04/ they also do a rear sprocket with three teeth less as well as a selection of front sprockets Link to comment Share on other sites More sharing options...
Paulwhite Posted April 30, 2010 Share Posted April 30, 2010 where were you oldtimer when i wanted to do the same on my dragstar!!!! i looked everywhere for about 3 months to find one and could only find somewhere that built custom sprockets but saying that it was about 2-3 years ago. sorry reservoir dog i stand corrected! Link to comment Share on other sites More sharing options...
oldtimer Posted April 30, 2010 Share Posted April 30, 2010 reservoir dog , hi juan heres that link to the topic on sprockets it was a guy who wanted to do the same as you hope this helps. its on page two to save you reading it all. Link to comment Share on other sites More sharing options...
Reservoir-dog Posted April 30, 2010 Author Share Posted April 30, 2010 I have no doubt that the this little big bike could improve it's performance by ticking with the gearing being the easiest way starting by changing the front sprocket. First of all because the transformation remains hidden (no obvious need to inform your insurers LOL) as well as little changes need to be made to the chain (wheel/chain adjustment will allow that). My big question is 1 or 2 teeth? Unfortunately I haven't yet found a bike guru in London that could show me light in this particular dilemma. Link to comment Share on other sites More sharing options...
oldtimer Posted April 30, 2010 Share Posted April 30, 2010 In theory increasing the number of teeth on the front sprocket and/or decreasing the number of teeth on the rear sprocket you will result in higher top speed, lower acceleration and better fuel economy. And vice versa: decreasing the number of teeth on the front sprocket and/or increasing the number of teeth on the rear sprocket will result in lower top speed, higher acceleration and worse fuel economy. However whilst generally true in practice this is not allways the case, mostly due to the power output of the machine at certain revs being higher or lower than at others. to achieve your desired result will often involve some trial and error. It should also be noted that some models cannot accommodate larger front sprockets but in the case of the xvs dragstar 125 this is not a problem as it will accomodate these changes without the need for any alteration of the chain. one or two teeth? well as the gain with one tooth is so minor i would be inclined to go +2 on the front sprocket and maybe less 3 on the rear sprocket as with Lowering the ratio increases top end speed - Increasing the ratio increases acceleration and bottom end power you will get the maximum benifit but like the guy in the link i gave you it is a matter of trial and error and as i have been happy with the performance of my 125 i have not done any modifications i can only go of what others have done, when i feel the need for speed and an adreniline rush i get on my fz. Link to comment Share on other sites More sharing options...
Reservoir-dog Posted May 1, 2010 Author Share Posted May 1, 2010 Thank you very much Oldtimer you are absolutely right. Is a matter of trial and error. I'm inclined to go +2 on the front sprocket to start with and see how it goes. To me is not a matter of more speed is a matter of achieving the same speed with less revs therefore making the bike even smoother when cruising. Today for example I did a stretch of the North Circular Road at about 50 mph (I was going to the Ace Cafe but turn back due to rain LOL) and I found myself looking for another gear as I though that I was in 4th. I also noticed that cruising in 5th under 30mph, like my bike does comfortably, is not quite right. I honestly think that the guys at the factory panic a bit when they had the idea of making a 125 on a 250 frame so they gave it to much ratio. Thanks all for tips Link to comment Share on other sites More sharing options...
jerc Posted May 2, 2010 Share Posted May 2, 2010 this thing is very interesting for me also:) reservoir-dog keep us informed how the thing works out for you i'm thinkig to do the same thing...but it's harder to find these parts here in Slovenia and i think i'll have to order them from somewhere else which costs me a bit more;) that's why i would like to hear something from you first. Link to comment Share on other sites More sharing options...
Reservoir-dog Posted May 9, 2010 Author Share Posted May 9, 2010 Update A decision has been made. Definitely 2 tooth up front sprocket (from standard 16 to 18) is the way to go to achieve the improvement I'm seeking. Thanks to oldtimer that direct me to this link http://www.yamahaclu...oke/page__st__3. No need to invent what already has been invented and tested. Fantastic job and shared information by Markyboy27. However there are some modifications that Markyboy27 did that I'm still not 100% sure, as for example the removal of the in line fuel valve. I just don't understand what this valve does and why it restricts fuel to carburettor. So I still have to workout that one. Regarding the EMGO air filter is another one I'm still not sure if it make that much difference. I've owned, and fiddled, in the past with a VW and a Porsche 912 flat four air cool engines and to my experience this K&N filters never really shown a noticeable improvement in performance. In another words a decent or stock filter did the same. Yes they may do but together with another modifications like polished intake manifolds, polished heads, bigger valves and bigger bores. Regarding what Markyboy27 did about jets (100 jet to replace 90 standard) I agree 100%. I know every bike , even same make and model, is different and feels different but based on my bike my opinion is that the xvs runs to lean. Take for example the time that you need to maintain the choke on until the bike runs smooth. To me means to much air/to less fuel and therefore a bigger jet will cure that. So maybe no need for alterations with the air filter but definitely with the main jet. There are a lot of people questioning, in this and another forums, if the xvs is somehow restricted. My answer would be yes by the meaning of lower gearing and jet carb restriction. Tomorrow I will order my 18 tooth front sprocket. I will then run it to get the feeling of the changes. The chance are that by the 25th May, MOT time, I will have the jet replaced. As I said above I think that the guys at the factory panic a bit when they had the idea of making a 125 on a 250 frame. I will keep in touch Link to comment Share on other sites More sharing options...
Reservoir-dog Posted May 25, 2010 Author Share Posted May 25, 2010 Update Today I had the stock 16 tooth front sprocket replaced with a 18 tooth one and what a joy: The best decision ever. It's like riding another bike but better. So much smoother. Beautiful engine balance through the gears and cruises at the same speeds with much less revs. To give you an idea I would say that now I can cruise at 30 Mph in 4th with less revs then before in 5th and somehow when you accelerate it feels like you have more torque, and when you change to 5th.......Heaven.... really smooth. You don't get the feeling of loss of power whatsoever. Guys and girls I recommend this easy and inexpensive transformation that doesn't even involve fiddling with the engine. Total cost was: Supplying the front sprocket (them not me) Labour to replace the front sprocket MOT Engine oil top-up (serviced last month) £60.00 The next and final chapter will be the main jet replacement from stock 90 to 100. I will keep you guys informed. Link to comment Share on other sites More sharing options...
neversaydie Posted May 26, 2010 Share Posted May 26, 2010 Update Today I had the stock 16 tooth front sprocket replaced with a 18 tooth one and what a joy: The best decision ever. It's like riding another bike but better. So much smoother. Beautiful engine balance through the gears and cruises at the same speeds with much less revs. To give you an idea I would say that now I can cruise at 30 Mph in 4th with less revs then before in 5th and somehow when you accelerate it feels like you have more torque, and when you change to 5th.......Heaven.... really smooth. You don't get the feeling of loss of power whatsoever. Guys and girls I recommend this easy and inexpensive transformation that doesn't even involve fiddling with the engine. Total cost was: Supplying the front sprocket (them not me) Labour to replace the front sprocket MOT Engine oil top-up (serviced last month) £60.00 The next and final chapter will be the main jet replacement from stock 90 to 100. I will keep you guys informed. I agree. I changed mine last weekend. The one that I took off was 15 tooth, so I've actually gone up 3 to 18. Its like having another gear available. Cruising now at 60-65 with plenty left, longer to accelerate but still able to accelerate with traffic flow easily. Yes, I have also noticed that the engine performance is smoother both up and down through the gears. Total cost £7, money well spent. Link to comment Share on other sites More sharing options...
Reservoir-dog Posted October 12, 2010 Author Share Posted October 12, 2010 UPDATE Finally I had the main jet replaced together with a new smaller rear sprocket. So the modifications so far are as follows: 2 up in the front sprocket (from 16 to 18) 2 down in the rear sprocket Main jet replacement (from 90 stock to 100). End result? Guys, if you own a xvs 125, my honest advice is, go for it. You won't regret it. My bike is now much smoother, more ridable and faster. Just to give you an idea, I can now cruise at 40mph in 4th with more or less the same revs that I used to do in 5th so if I now shift to 5th I still cruise at 40mph but with less revs but with a much smother ride and plenty more speed if I just decide to rev. My mechanic thinks that the funny whistling noise my engine is making when hot is due to an exhaust leak (see my other thread) so I will look into to that but as far as changing the ratio and jet is concerned I'm extremely happy. Link to comment Share on other sites More sharing options...
Paulwhite Posted October 12, 2010 Share Posted October 12, 2010 just do me a favour and keep a CLOSE eye on the oil quality! all these mods will wear down the piston rings a little faster (and replacements are like gold dust) plus if the oil quality goes down the toilet so will the bottom end! (trust me iv had 2 engines fail on me at the crank!) so yeah good job! just keep an eye on it Link to comment Share on other sites More sharing options...
Reservoir-dog Posted October 12, 2010 Author Share Posted October 12, 2010 just do me a favour and keep a CLOSE eye on the oil quality! all these mods will wear down the piston rings a little faster (and replacements are like gold dust) plus if the oil quality goes down the toilet so will the bottom end! (trust me iv had 2 engines fail on me at the crank!) so yeah good job! just keep an eye on it I will Paul. Can you recommend some good oil? Link to comment Share on other sites More sharing options...
JohnnyK Posted October 14, 2010 Share Posted October 14, 2010 I am having these mods done tomorrow as well. I'm also fitting a HiFlo oil filter, new plugs, a new stock air filter and a new chain w/ rear sprocket. I'm hoping it will feel like a brand new bike will let you know how I get on. At the moment I do around 30 miles a day on the A3, and at 50mph I either have to be at extremely high revs in 4th, or I change up into 5th only to suffer a loss of power/speed, meaning I'm constantly shifting to maintain speed. Anyway, will let you know how I get on. Link to comment Share on other sites More sharing options...
Paulwhite Posted October 14, 2010 Share Posted October 14, 2010 I will Paul. Can you recommend some good oil? i dont know m8 iv not looked into quality oils yet (its a big subject) but ur looking to spend around 30-40 quid + a liter for the TOP quality stuff but i couldnt tell you what to get. but if you get some medium good oil say dont spend less than £15 a liter but just do an oil change every 4-6 months then it should be ok ur best bet would be to ask around on the forum or pm the moderators on here as they will be able to give you a better answer with there years of experience! and im sure a question like this has been posted in the past. i know 10w 40 is the basic but you get different tipes/viscosity depending on weather conditions so since were coming into winter you want one suited to both the bike and the weather conditions. (to the moderators if they read this) would it be a good idea to pin up some links or some info on quality oils? like viscosity charts, what makes would be best for certain weather conditions and even some hands on experience of oils? and possibly some rough prices of what you would be expected to pay for quality oil? Link to comment Share on other sites More sharing options...
neversaydie Posted October 14, 2010 Share Posted October 14, 2010 Silkolene Super 4 10W40, at around £6 per litre. It's vital to have the right type of oil, and that its changed regularly with the filter. Exposed electrical contacts (regulators/rectifiers etc), spray a little WD40 or similar moisture repellent. Link to comment Share on other sites More sharing options...
Reservoir-dog Posted October 14, 2010 Author Share Posted October 14, 2010 Paulwhite sent you a PM Link to comment Share on other sites More sharing options...
littlepig Posted October 20, 2010 Share Posted October 20, 2010 Troops what's the 3 teeth less on the back cog do for the performance ? I'm already 2 up in front sprocky, is it worth doin? Link to comment Share on other sites More sharing options...
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