Yamaha Virago XV 125 air fileter/carb/sprocket modification.

[El Muerte]

Ok new update for all Xv 125 enthusiasts.

There was a lot of work once I told my mechanic I want him to install performance air filter and re-jet.

He dismounted and put back carb. at least 10 times.It was hard as hell to find right mixture, so guys don't do this at home.It is at least 10 times trickier than XV250 carb re-jetting.XV 125 is much more sensitive.

I also modified my front sprocket and changed from 13t to 14t.

With new air filter and re-jetting, my little Virago goes slightly better with 14/47 compared with stock 13/47 (no air fileter mod).

Yesterday I took her for a ride, and boy does she sound different.....

Cruising speed is now 65-70 km/h with no problem at all.

Every gear is longer about 10km/h, so now when I shift to 5th, it becomes cruising gear......low acceleration but it goes 70km/h with lower RPM (-1000 RPM's by gearing commander calculator)

This mod is really good for longer trips, altought my cruising speed is better, my maximum speed is lowered compared with stock 13/47.

Now it is 90km/h.

Reason for this is weak torque on all 125cc engines.It's just to hard for poor xv125 to withstand weight of driver and wind resistance at 90km/h.

Remeber this is only with 14t sprocket mod, the motorcycle will go much faster and have much much better acceleration, and of course it will go much better uphill if you just modify air filter and carb, but keep stock sprockets.

Point is, this mod will give your XV125 more power !

Now I wait to see what fuel consumption I'll have.

Gonna keep you updated guys.......

P.s How to correct spelling in topic headline ? I made slight typing mistake up there

[Paulwhite]

hi there iv got a Sachs roadster which uses the xv 125 engine and have tried to re-jet it about 12 times now!!!

i went out and baught a shorty k&n style performance air filter off ebay, and have had to connect it to the airbox instead of on the carb. it originally had a 77.5 main jet and now is running on a 97.5 the bike runs fine but is too on the lean side for my liking, plus i have to run it up and down the street just to get it started! so could you tell me what size jets you used? what air filter you used (if any)? and if you have changed the exhaust at all?

cheers. Paul .

[barwell1992]

whats the speed taken from on these bike ?? if its a wire to the front hub then thats fine but if its the cdi unit that reads the speed changing the sprockets will alter the bikes speed reading as it will be doing more or less than it would have been at stock due to the diforent sprockets

not sure if this is the case on this bike but it is on mine unfortunatly

[El Muerte]

what air filter you used (if any)? and if you have changed the exhaust at all?

cheers. Paul .

I used Delo Performance Air Filter, bought in Germany/Louis store.Looks just like K&N filter.

For jet sizes, I affraid I can't help you with that, becouse i left my bike at mechanics.......BUT he did mentioned that mixture was too lean at one moment and he used very small drills to make jets a bit bigger (not to much).

So use smallest drill you can find and start from there.Find the size that is same size as jett hole,and make it bigger just a bit (0.5mm)

Then clean everything, put thogether the carb, and give it a try.If mixture is to lean, repeat again with bigger drills.

@barwell1992

My speed sensor is monuted on front wheel so no worries there

But Im not lookin for maximum speed.Yes it's true, bike can go faster but when you go around 100km/h the engine screams in high RPM's, so you can't drive like that.What I did is I changed front sprocket not go gain maximum speed but to lower RPM's at 70km/h.Now on 14/47 setup at 70km/h it's same engine stress as it was with old non modified 13/47 @ 60km/h.

Of course I had to modify carb and air filter to compensate for acceleration losses, and to relieve engine from stress.

[Paulwhite]

cheers but i cant afford the jetting kit at the mo, and at £1 per jet i cant really grumble

but my idea is to give the engine a little more power then fiddle with the sprockets to decrease the revs

where did you find the front sprocket? cause i cant find any non standard ones anywhere!

and how is your air filter fitted? is it straight on the carb or in your airbox?

a new exhaust is on the cards but am having trouble getting hold of the rear cylinder header.

.cheers . Paul.

[El Muerte]

cheers but i cant afford the jetting kit at the mo, and at £1 per jet i cant really grumble

but my idea is to give the engine a little more power then fiddle with the sprockets to decrease the revs

where did you find the front sprocket? cause i cant find any non standard ones anywhere!

and how is your air filter fitted? is it straight on the carb or in your airbox?

a new exhaust is on the cards but am having trouble getting hold of the rear cylinder header.

.cheers . Paul.

First of all you don't need jet kit, just set of drills ))

For sprockets look at www.jtsprockets.com they have everything you'll need.

My air filter is fitted directly to frame of the bike.Entire casing is stripped, and custom filter is placed.

Also, be reminded that there are 2 restriction rings on exhaust.Remember that the engine is like a pump.It wont breathe properly.

Check the header pipe near the engine, not the muffler, and then remove thoose rings (rear one is welded, so use a metal file to remove the welds)

[dogmeat]

Also, be reminded that there are 2 restriction rings on exhaust.Remember that the engine is like a pump.It wont breathe properly.

Check the header pipe near the engine, not the muffler, and then remove thoose rings (rear one is welded, so use a metal file to remove the welds)

Sorry to butt in here but I have a xvs 125 and was interested in these 'rings'.

Are you saying they are between the header pipe and the engine head?

How do I get the headers of they seem to have a funny star shaped bolt on them.

Please help a noob.

[El Muerte]

Sorry to butt in here but I have a xvs 125 and was interested in these 'rings'.

Are you saying they are between the header pipe and the engine head?

How do I get the headers of they seem to have a funny star shaped bolt on them.

Please help a noob.

That funny shaped star-head are known as torx screws, wich are quite often on cars and motorcycles.Factory places them becouse they don't want to fumble around exhaust pipes.

Don't know if Dragstar 125 have restriction rings, but by looking on pictures of rust you have there, it would be recomended to use anti-rost spray, and later grease them for easier unscrewing.

I suggest you look air filter casing and intake manifold aswell.

If you find some restrictions, after you remove them, you better re-jet your carb or your mixture will be to lean.

[snoozieboi]

Hi El Muerte

This is not meant to hi-jack your thread, but to add to your information I found a very similar mod on http://www.up-power.eu/shop_view.php?idpro...&codecat=38 (which is a filter, sprocket and jetmod, i think) They've got english pages but these are outdated.

This is supposed to give you a ~14hp engine according to their graph from their DynoJet (dynamometer machine for cars and mc's)

I've emailed the guys (that are french, using google translate:)) they've made the mod themselves and offer customers a refund if we're insatisfied with the results. Personally I just drove 700km in 3days with my Virago '97 125xv after storing it for 6 years in my parents basement. If my virago could do 80kph instead of 70kph against the breeze/uphills I'd be a happy rider.

There's nothing more stressing about this bike than cars closing in on me from behind in Norways everlasting hillsides, I find it pretty embarassing to since the bike probably looks like a regular chopper.

My hope is that someone has tried this mod or is able to do research in french forums about this mod, I'm not that good at modding my bike either, it's bog standard still.

snoozieboi

[frankg]

For anyone who has a Virago XV125 then this thread will only add to their frustrations cos when you search the net there is sweet eff all on the market to increase power only limit the vibration increase torque (no real problems there anyway even as standard) and reduce fuel consumption and make it sound and look better.

The only excuse to rejet is if your using aftermarket exhausts and or air filters like the Highway Hawk or the even more expensive Silvertail sound awesome but give no extra power. The guys who have the 250s and especially the CHinese Lifans have tried everything but really the benefits are marginal at best. You can drill out bafflers and air restrictions but they dont really do all that much as those who have tried have found out - even trying to change the carbs - nothing zilch. Except a big hole in their wallet. Even to rebore it out to its max hasn't worked particularly well some have even tried to have their CDI remapped - again NAWT or nothing that really makes it worth your effort.

My son has one and we know quite a few others who also own them or have in the past and its more amazing to know one bike might do 70mph and others struggle to do 65mph, and all as standard. No 2 engines are ever alike thats a known fact and in these cases a good one is well worth seeking out. My son is a sod like everyone else for wanting to squeeze every extra mph and it really is a struggle,

Im sure if anyone had solid cast iron info on what to do it would be all over the net, it simply isnt, just a lot of people asking the same questions - can it be done and how. After all its a big lump so why not 80mph or above not the rated 63mph as Yamaha state the xv125 can reach, some get 70mph on the straight. Cos you cant, CAN YOU????? Add a nitro kit, supercharger and gasflow your heads haha............ put a 250 block in they do 23mph more rated at 85mph (some do over 95) - its a straight swap for the whole engine carbs and CDi, everything else is the same - cost you as much probably as your bike is worth or in some cases even more.

[snoozieboi]

Sorry to add to your frustration Frankg, I know this is a typical question, but did you read my post carefully?

I'm talking about kph not mph, I'm trying to get torque rather than top speed. I'm trying to follow regular traffic uphill rather than over take regular trafficers.

up-power's kit costs 79Euros, hardly a hole in my wallet, they claim they've got a dynamometer for testing of their own solutions and the graph to prove it, otherwise I get my money back if I'm not satisfied. Now, why these guys should get more power out of the engine than the actual manufacturer is a good question, and can probably partly be answered by Yamahas wish to make a longer lasting engine.

I'm of course willing to risk 79 euros to be able to to 50mph (80kph) uphill or against the breeze and was hoping that some others had done it before me and were able to report back on the results.

[rats]

hi there iv got a Sachs roadster which uses the xv 125 engine and have tried to re-jet it about 12 times now!!!

i went out and baught a shorty k&n style performance air filter off ebay, and have had to connect it to the airbox instead of on the carb. it originally had a 77.5 main jet and now is running on a 97.5 the bike runs fine but is too on the lean side for my liking, plus i have to run it up and down the street just to get it started! so could you tell me what size jets you used? what air filter you used (if any)? and if you have changed the exhaust at all?

cheers. Paul .

hi i have a sachs 125 v-twin, that uses the virago engine.. yes ive had problems too, some one nicked my bike and i found it down the road. i think they dropped it, it smashed my carb, and left a crack in it.. after much running around for a carb, i found out that they stopped making that carb 12-13 years ago. seeing as the carb is a side draft, finding one that fits the gap between the intake maniflod and the stock air box was impossible, unless you fit theses new C.V carbs, but it needs a fuel pump and the bike dont have the electronics to connect a fuel pump.. i had got a suzuki gs carb, and a swiviel manifold, and bypassed the air box, with a k n filter.. yes it was very lean at first, then it was too rich, only to find out its running rich and lean due to the k n filter sucking in to much air.. i had to stuff the filter with rags to restrict the amount of air to the carb.. now i have to say it runs well. normal cruzing speed 50-60 the bike can reach 80-90 but i dont do it often

hope this helps others who had air filter probs

[Paulwhite]

hi i have a sachs 125 v-twin, that uses the virago engine.. yes ive had problems too, some one nicked my bike and i found it down the road. i think they dropped it, it smashed my carb, and left a crack in it.. after much running around for a carb, i found out that they stopped making that carb 12-13 years ago. seeing as the carb is a side draft, finding one that fits the gap between the intake maniflod and the stock air box was impossible, unless you fit theses new C.V carbs, but it needs a fuel pump and the bike dont have the electronics to connect a fuel pump.. i had got a suzuki gs carb, and a swiviel manifold, and bypassed the air box, with a k n filter.. yes it was very lean at first, then it was too rich, only to find out its running rich and lean due to the k n filter sucking in to much air.. i had to stuff the filter with rags to restrict the amount of air to the carb.. now i have to say it runs well. normal cruzing speed 50-60 the bike can reach 80-90 but i dont do it often

hope this helps others who had air filter probs

god its been a long time since i left that post lol but yeah iv fitted a dragstar 125 carb its a bit tight but it fits (just) found its exactly the same just the part where the end of the throttle cable goes is on the other side but im gonna try and swap it round if i cant then itl still work. but yeah i found that the engine runs loads better with the airbox! rather than an air filter. plus iv figured out it wasnt the carb causing problems it was me piston rings so the bike is now off the road whilst i try and source some parts iv tried cmc and there crap! said they need the virago frame number to find the piston rings even though its just the engine iv got!!! so going to go and get mugged at the sachs dealer (they charge stupid amounts!) lol

[scifi]

Hi folks im new to this forum but iv poked and prodded a lot at my xv125, and i have good results and solid info if you want more from it, iv gone to extremes tryed a lot ..but this works without any flaws and i did over 2000 miles this year on this configuration.

I shall state what has been done in a moment.

a few points to note.

(1) The xv125 has no exhaust restrictions. (the exhaust is exactly the same part as the 250 although moding it slightly does help.

(2) The cdi is important it needs to be a tnd45f all other cdi units are limited to around 8500rpm the tnd45f has a upper limit of 10500.

(3) The air box. The air flow is critical, the engine needs the back pressure.

(4) you cant beat a good service.

(5) use standard gearing

okay i`l begin on what i get out of my xv125 on the flat i can hit 60mph in 4th, with a good long road in 5th i can hit 72mph. up hill i can easily hit 50mph.

okay first and most important of the modifications is a simple one, the standard main jet is a 76.5 if my memory serves correctly from when i removed it...replace this with a 90.

Within the air box of the 125 there is a tube for the air intake which is halved off (this will make sense if you`v seen it)

do not make it circular remove a slither (literately only a millimetre) off the half that exists (DO NOT REMOVE ALL THE FLAP)

this ones a bit more scary ...i used a VERY large sharpened screw driver about 7/8 mm in diameter (thats about 3~4mm less than the hole at the end of each silencer), with this insert it into each silencer and knock through...and make sure you count...1 baffle plate there are more but one will do other wise instead of increasing the flow of air you will just end up with no back compression at all..

hope this helps all them that want a bit more poke.

Any questions feel free to ask.

Sci

[scifi]

Oh and if you can get your hands on the 6 spoke alloy mag wheels they did on the very last years production they shed a load of weight.

[El Muerte]

Hi folks im new to this forum but iv poked and prodded a lot at my xv125, and i have good results and solid info if you want more from it, iv gone to extremes tryed a lot ..but this works without any flaws and i did over 2000 miles this year on this configuration.

I shall state what has been done in a moment.

a few points to note.

(1) The xv125 has no exhaust restrictions. (the exhaust is exactly the same part as the 250 although moding it slightly does help.

It does , well mine did at least and it is at begining of exhaust , when you take down the washer.Just before the enternance, there is small plate-ring that restricts gases to get out.

Something like this:

http://members.modernvespa.net/xantufrog/uploads/restrictorconeremoved_197.jpg

[El Muerte]

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http://viragotechforum.com/viewtopic.php?f=88&t=21116