Tommy Boy Posted July 2, 2011 Share Posted July 2, 2011 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. Link to comment Share on other sites More sharing options...
Tommy Boy Posted July 3, 2011 Author Share Posted July 3, 2011 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 Link to comment Share on other sites More sharing options...
root Posted July 5, 2011 Share Posted July 5, 2011 To fit a 99 Sr engine in a 95 , you either need the 99 wiring loom with it, or fit the 95 stator with cover & also the flywheel in the 99 engine . Link to comment Share on other sites More sharing options...
Tommy Boy Posted July 9, 2011 Author Share Posted July 9, 2011 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 Link to comment Share on other sites More sharing options...
Tommy Boy Posted July 9, 2011 Author Share Posted July 9, 2011 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. Link to comment Share on other sites More sharing options...
Tommy Boy Posted July 15, 2011 Author Share Posted July 15, 2011 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. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 15, 2011 Moderator Share Posted July 15, 2011 Great news well done, that 'broken man' thing had me nearly But now I'm all happy again. Link to comment Share on other sites More sharing options...
tez73 Posted July 15, 2011 Share Posted July 15, 2011 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. try spraying some easy start into where the air filter fits to the carb as you are turning it over? terry 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. Link to comment Share on other sites More sharing options...
Dave Jones Posted May 11, 2018 Share Posted May 11, 2018 On 7/15/2011 at 9:10 PM, Tommy Boy said: 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. im just doing this at the minute and seem to have similler problems, ive got a 2002 bike which has dropped the exhaust valve, so ive got a M reg 1995 engine which i have seen running fine and put that in, i have swapped the left hand casing and flywheel, so all the wiring matches up with the cdi etc, problem i have now is im getting a spark, got fuel, checked valve settings and timing and its all coming back fine, im slowly at a loss, ive got some spares so iv swaped, the carb, the coil, plug, cdi, etc to no avail. still the same issue, my next logic would be to say that the ignition timing could be out? can anyone help me on this? Cheers Dave 1 Link to comment Share on other sites More sharing options...
Moderator Cynic Posted May 12, 2018 Moderator Share Posted May 12, 2018 We can definitely help, the problem being you have tacked on to a frankly ancient thread. Your chance of a response is low at best. Go for a bit of an intro in the new members area then kick off with a proper thread of your own in the 'workshop' area. I will lock this one. Link to comment Share on other sites More sharing options...
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