Tommy Boy

I've looked into this in the past. Personally I'd go for a decent brand Xenon. I was going to fit one to my SR125 but the older model doesn't take H4 bulbs. But without messing around with HID kits I doubt there are many options. If you are going to just upgrade the bulb, spend a bit of money. I've heard from too many people that the cheaper bulbs blow incredibly fast.

Ok guys got some good news. Managed to get the bike going and running ok(ish). I'm pretty sure that it's within the bikes nature to be a bit lumpy on the idle speed and fluctuate slightly with occasional cut-outs and if this is the case then my problem could very much be sorted. If someone has a second opinion on this please advise. How did I do it? Well strangely enough after another attempt at playing with the carb, I fitted the jets and screws that looked in best shape, then set everything as close to factory setting as I could. After a few coughs and splutters a friend told me to disconnect the breather pipe (the one from the engine to the air box) and low and behold the bike fired into life. I couldn't quite understand why it was this that was giving me the grief but whenever it got reconnected the bike would go straight back to lumpy and cut out. I decided an oil change was necessary as it was reading slightly over and upon draining the oil i noticed that it seemed as if the oil had turned into a petrol mix. It was watery and had no real resemblence to oil any more. Anyway I stuck fresh oil in it and still had no luck with running it however things did seem to improve slightly. So I took the bike up and down the alley a few times with the breather disconnected then stuck it back on after a few runs and the bike didn't seem to mind. I took it for a few more runs up and down and the bike performed very well. So i spent a bit more time and adjusting the carb whilst running and tried to get the idle speed down nice and low without it cutting out. Now I haven't had the chance to let the bike cool and try restarting it but I will let you know how i get on once i try it. My only concern now is that the first part of throttle is a bit lumpy and the bike cuts out every now and then. The mixture screw seems to have no effect on the running what so ever. Does anyone know if it's knackered and needs replacing? Or am i just not paying attention. I screwed the mixture screw all the way in and it had no effect on the speed or tone of the engine. To be honest I'm more then happy with the bike as long as it starts for me next time I try it but I would like to iron out these last few creases. If anyone can assist I'd be very grateful. Cheers all

I'm with Airhead. The +ve feed sits at the relays contact until the relay is energised, where it is then given a path to the bulb. By connecting the heated grips here you are just sending the same voltage down two separate paths - The grips, which get a constant supply (as long as ignition is on), and the brake light (When the brake relay is energised). Pulling the brakes has no effect on the grip circuit (apart from a slight current draw but I doubt it). I do understand the confusion though. Madison, if the grips were hooked up on the contacts other side (87) then it would have the effect you're talking about. As far as the best place to connect goes, it depends on how fussy you are and what wires are easiest to get at. I'd personally go from somewhere on the switched circuit that has thick enough wires and before any fuses but like I said i don't know bikes (let alone 'the' bike) well enough to comment. Airhead seems to know his stuff.

Spot on Airhead. Let us know if they're any good dewang

Sorry airhead I completely missed that. Also would that cause the engine to throw fuel up into the air box? I'll see if we've got any feeler gauges. Pretty sure its 0.8mm for my bike. Gunna look up how to do it now.

Messed around with float heights today and still no joy. Managed to get the bike starting but i had to have it on full throttle all the time while turning the engine over to get it fired up, then from then on it would run really lumpy and kick out a load of petrol from the air filter box. If i let off the throttle it would just cut out. Tried both carbs on it and there wasn't much difference when it came to starting it. Like i say, it was just about running on full throttle which is better then nothing but it's no good to ride. Is it time to consider taking it to a bike garage?

I'm guessing the starter relay is for the starter motor. Just connect it to the live coming from (not to) the ignition switch. Couldn't tell you colours as i dont have a YBR or manual. But by doing this you don't risk leaving them on and draining your battery. If you upload the circuit diagram I might be able to help you further but it will be down to you to relate the diagram to the bike itself

Hello Jimmy and thanks so far. As far as the electrics go on these bikes, the only thing that's different engine wise is the generator (and the fact the carb has a heater). My bikes a W reg (94/95) and the engine i think is A 99 But I can't remember. It's certainly the newer model. As far as I'm aware as long as the new engine has an old generator fitted, the bike should run ok. I've kept all the old electrics on the bike the same so the cdi, distributor ect are the older type. I did have the bike running ok with the new engine, and the old carb fitted so I'm assuming its just the settings on the carb that's causing me grief. Anyway i'll check out the float heights, adjust and put every thing else back to factory settings. Hopefully this will moves things forward. Cheers!

Hello all and firstly thank you for having a look at this thread. I'll just give you all a brief insight on what ive done so far just incase i'm looking in the wrong place. So i started off with a rattly old SR125 with high milage so i decided I'd give it an engine change. I sourced an newer engine complete with carb with a low unconfirmed milage. I couldn't get it running at first, then i discovered the electrics were different. After replacing the generators over, i still had no luck. I then looked at all the other easier possibilities like compression, spark ect before i narrowed it down to the carb. I stuck the old carb back on and hey presto the thing fired into life after i bump started it. A while later I decided id probably get more out of it if i tried getting the newer carb fitted and running. So i counted the turns on the old and messed about with stripping both of them, cleaning them and everything i shouldnt really do, then once i reassembled both carbs neither of them would work. Now here's the latest. With the new carb cleaned and with the 108 main jet from the original carb fitted (new carb came with a 102. Anyone know why/if this will cause issues) and the throttle screw mostly out and the pilot screw 1.5 turns out i tried bumping the bike. I got alot of spluttering. I tired multiple times each time either turning a 1/4 in/out or with the choke half/fully out. The most i got out of it was about 4 seconds of the bike running before cutting out and throwing loads of petrol out of the air filter drain tube. After doing a lot of reading i think the fuel pouring out of the air filter is related to do with the fuel level in the carb/float height. Can someone please confirm this? Will this cause a rich mixture and prevent it from starting? As far as I'm aware the fuel inlet valve and needle aren't worn. The floats are in good condition but im pretty sure their height is the issue. I read in the haynes that you can do a check without taking the carb off but it involves clear plastic tubing and the black bit of pipe that hangs from the drain part of the carb is missing. Checking the float heights I can do but it just doesn't seem like a very accurate way of doing it. Any way what do you lot think? Am I looking in the right places? Where should I start. Just to confirm - when trying to jump the bike, it very rarely starts, mostly splutters, and when i got 4 seconds of revving out of it it cut out then dumped a load of petrol on the floor from the air box. all the jets are clean and the floats aren't damaged but i think the heights definitely need looking at. Does this sound correct and if so what the most accurate way to measure?

Thank you all. I'm in Luton although you probably wont see me on my bike just yet. Got a problem with fuel in the air filter (carb i believe). I'll be doing my test in Hemel Hempstead.

Hello all, I remember subscribing here a while back now but cant remember whether I introduced myself and haven't been on in a long time. Firstly my name is Tom and I own a SR125. I've only got a CBT but I have my bike theory tomorrow and have my mod 1 booked for next week. I have been riding for less then a year but i have to say that it is the best form of transport. After playing around on a bike I was convinced I wanted to give it a go so i went and got myself on a CBT. I spent a good couple of months cruising around on my bike until i decided to do an engine + carb swap. Since then I haven't really been out on the roads much mainly due to distractions keeping me from working on it. Recently a friend of mine acquired his full licence and after taking me for a spin i decided its definitely something I enjoy and so I've decided to get well amongst it again. My short term goals are to get my SR125 fully fit again (carb issues) and also get my full licence within the next few weeks. I'll probably open a new thread relative to the issues im having with my bike so please feel free to have a look to see how im getting on I hope that I can bring something to this place. I work with electronics so if anyone needs anything explaining please dont be afraid to ask me questions. I will do my best to help where I can. All I need to do now is sort this bloody carb out. Thanks for looking Tom

Name: Yamaha SR125 (1995) Date Added: 31 October 2012 - 08:14 PM Owner: Tommy Boy Short Description: Bit of an old chugger. When i first got it I decided to put a newer engine on. After sourcing one with an unconfirmed low milage but spotless casing i managed to fit but could only get it running with the old carb. Now im in the process of trying to get the new one fitted. Watch this space View Vehicle

Ok after much digging i've discovered that all after market kits aren't exactly legal however the law do very little and don't really know the difference or how to check whether they have or have not been tested in a certified 'laboratory' in order to make them legal. So from what i've gathered i can say that you can get away with fitting the kit and not get bothered by the law. Anyway to save myself that small risk, i;ve decided to go with the blue tinted philips bulbs instead however now i have a new issues - I have the old head light on my sr125. Does anyone know if the old headlamp can house the new three prong h4 bulbs through adaptation? I'm pretty sure the three wires going to the old bulb will wire straight up to the 3 spades ok but im more concerned with the bulbs seating. I've looked at buying the newer model head lamp but I don't think it will fit, what with the speedo being different ect.

Check the bulbs first. If it's only jsut started since you changed them they'll be the wrong wattage. If they're ok then look at the earths. Flasher relay would be the last thing i'd suspect.

Thanks guys. I do try

Yes I took note of the bit where it said it's for off road use only. However the legal limit for headlights are 55w and these are well within the limit at 35w. Any other ideas on xenon lights or light upgrades for sr125's?

Hello all, I apologise for this post being late as I have already intruded upon this forum with questions prior to introducing myself, but better late then never. My names Tom, I'm 21 and recently passed my CBT. I am looking at doing my full bike test however for the time being im just enjoying my 125 and learning the ropes of motorcycling. I also own a car and have been driving for a couple of years now so have some appreciation of the road. I have an interest in mechanics and work with electronics which is very handy. I recently carried out an engine swap on my bike which after much sweating and swearing, i managed to get it going and road worthy. Im currently looking at upgrading my lights but i'm not very experienced so once again i've turned here for assistance (another topic). Thanks for all your help so far. I look forward to having some input to the forum. Tom

http://www.ebay.co.uk/itm/H4-3-Hi-Lo-Motorbike-ATV-HID-Xenon-conversion-kit-/280528087355?_trksid=p5197.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D3%26po%3DLVI%26ps%3D63%26clkid%3D1619872333330972788&_qi=RTM742988#ht_2096wt_1139 Here is a link to one of the upgrade kits i've been eyeing up.

Hello all. I own a 1995 SR125. I'm looking in to upgrading my headlamp. I've glimpsed at just replacing the bulb but after turning to a friend he's told me that they tend to blow and can melt the wiring and pointed me in the direction of costly conversion kits. He only has experience with car lights though. I've looked into both options and am not sure which road to follow. I've read a few posts on here that say people have simply replaced bulbs and that has worked wonders for them however i do like to do the job properly and am prepared to spend a little bit of money. The direct replacement bulbs i have looked at are the H4 ones going for about £5 on ebay but I'm unsure whether they'll fit, or whether they'll last. The conversion kits i've looked at are quite a bit more. Also I'm not sure whether they're compatible with an old 1995 SR125. Can any one shed some light on this topic? I've read through a number of lighting threads now but i'm after something more specific to my SR. Has anyone else tried or looked into this with theirs? Do i go with a replacement bulb or conversion kit? And what bulb/kit is the best for my bike? Is it even worth my while? All help is much appreciated. Tom

Changed the alternator/gen and the crankcase cover, and refitted the original carb, and after much continuity checking and pissing around, when i was on the verge of giving up and setting the bike on fire, i managed to get a splutter from the engine. I then gave her another go with the choke out and she fired into action. Voila! Moral of story is, when doing an engine swap on an SR125, ensure the bike you are fitting to and the bike the replacement engine came from have the same (think they changed in 97) or you will have to swap the alternator and sensors in the left hand crank case cover. And if you have compression, spark and fuel (After i swapped the alternator, it was the carb that stopped it from starting) then all it takes is a bit of trial and error and a lot of perseverance. Hope this thread sheds some light on the topic for anyone else who attempts an engine swap on an sr125. Apart from my dramas, its reallly not a big job at all and can easily be achieved in a few hours if you have the parts, tools and the know how. Best of luck all.

Is the flywheel connected to the alternator? Or is it the large cog behind it? If it's the large cog, why am i having to replace it? I swapped the stuff over (not sure about the fly wheel) and still nothing. I cleaned the new carb. Might give the old one a go but im honestly a broken man... I just can't figure it out. I'm getting super low ohms across the winding but i am sparking still. I just can't work out what's stopping it from firing. I have compression, spark and fuel. Maybe it's timing but surely it'd show some sign of life if that was the case. Someone please save me.

Cheers root just figured that out yesterday. Turns out it wassnt going to be as easy as just swapping over two sensors. Anyway my conclusion is this. To do an engine swap the bike and engine must both be either pre 97 or 97 onwards. If they aren't, like root said, you either need the compatible wiring loom and components or you can just swap the complete left crankcase cover and generator inside. To remove the generator on all models you will need a 16mm threaded bolt and another bolt approx 38mm with a 10mm head which has had the flats ground off so it's round. I'll post my findings once ive swapped the genny over so you guys can know it went ok for people in the future. On reflection, and engine swap on an sr125 really is quite easy if you have the tools to hand whether a genny swap is needed or not

Today i switched the carb with the old one to no prevail. I know the old carb is reasonably good because i had the old engine up and running on friday. From what i've done today i can only presume that the ignition system timing is the reason that the bike wont start. I don't get frequent paced sparks; instead i get a fluttering array of sparks with no constant timing. I believe the generator sensors on the 99 engine aren't compatible with the ignition system on my 95. I looked at the diagrams in the haynes and they too back this. I think the ignition unit needs replacing with what evers on the newer models (CGI unit or something) so instead, next weekend i am going to swap the left hand engine case covers (where the sensors sit) over to see if they are what's effecting the ignition. Please note today i carried out compression tests and also looked at the spark by resting the plug on an earth. I am presuming the carb is not at fault because it worked on friday with the old engine. The engine is not spluttering or anything. I poured a small amount of fuel directly into the piston head and tried starting and got nothing but a slight popping which is why i'm now (along with the dodgy spark) suspecting the ignition timing is my issue. If any one has any other ideas, please advise

After much frustration today, I have concluded that a straight swap is not feasible. Newer engines use slightly different ignition systems. Although the principles are still the same, the actuality is not. The sensors in the engine (brown green white and yellow/red wires) will throw off the ignition timing. I didn't have to time today but next weekend i'm going to swap the left hand cover of the old engine to see if that will solve my head ache. By the way all of the above is just my own personal predictions and experience and none of it should be taken as gospel. A lot of the above i have gathered from minor assumptions. But in relation to your question - Yes you can do a straight swap if the engine and bike are from the same era. however my bike is a 95 and the engine from a 99 is currently not working in it.

Hello all. I have swapped an engine from a 99 sr125 into my 95 sr125. The swap was plain and simple. The engine was sat for some time. Before doing the swap the original engine ran fine. Please note that the new engine came with a carb aswell which i fitted. The engine turns over but doesn't start. There is no indication of ignition what so ever. I have the electrics wired correctly and have fuel and oil. There is a spark at the plug but the engine will not start. The air filter is clean. All hoses are in good condition and are not kinked or blocked. The battery is or was charged. I have been persistent enough to know that a little more effort with trying to start it will get it going. I suspect the carb may be at fault. It may be the mixture or possibly even the timing but how do i confirm this and then sort it out? I still have the old carb and may re-attach it tomorrow to see if it helps but until then all suggestions are welcome.