SR125 - major start/idle problems

[sr125shell]

Hi, my SR125 is giving me a headache. It won`t start correctly.

Basically the only way I can get it to start without throttle is to fully turn the throttle stop screw adjuster all the way in (basically the same as giving throttle) but this leads to crazily high idle speeds & once I adjust the idle speed back to normal if I try to use the throttle it hangs at high revs for several seconds before attempting to idle properly again & the engine will eventually die + not restart without going through the whole procedure again. The choke doesn`t help starting at all.

Noticed white smoke from the exhaust also, but could just be condensation?

Carbs have been cleaned & floats, fuel mixture screw etc checked & set at correct heights.

Spark plug was carbon coated when I checked it (running rich?)

Air & fuel filters checked.

Throttle cable checked.

Any help with this is greatly appreciated

Thanks

Michelle

[drewpy]

Hi, my SR125 is giving me a headache. It won`t start correctly.

Basically the only way I can get it to start without throttle is to fully turn the throttle stop screw adjuster all the way in (basically the same as giving throttle) but this leads to crazily high idle speeds & once I adjust the idle speed back to normal if I try to use the throttle it hangs at high revs for several seconds before attempting to idle properly again & the engine will eventually die + not restart without going through the whole procedure again. The choke doesn`t help starting at all.

Noticed white smoke from the exhaust also, but could just be condensation?

Carbs have been cleaned & floats, fuel mixture screw etc checked & set at correct heights.

Spark plug was carbon coated when I checked it (running rich?)

Air & fuel filters checked.

Throttle cable checked.

Any help with this is greatly appreciated

Thanks

Michelle

could be worn valve guides/seals letting oil into the bore or worn bore/piston rings. a compression check for the latter and replacement for the former.

[sr125shell]

could be worn valve guides/seals letting oil into the bore or worn bore/piston rings. a compression check for the latter and replacement for the former.

Thanks for the reply Drewpy, I`ll do a compression test as soon as the adaptor comes for my compression tester for motorbike spark plug sockets. I`ll check my Haynes for info on valve guides/seals.

I forgot to mention that the year of the bike is 2003 & it`s only done 3000 miles - all done by the previous owner! Is that too soon to expect things to be wearing out?

Michelle

[fosdyke]

Hi

You didn't say how long you have had the bike and if this is a new problem.

If the the smoke is blueish white and you get clouds of it when you first start up it sounds like valve stem, or seal wear, not really good for 3000 miles!

When you checked the throttle operation did you observe the card operation at the same time? - sounds like the throttle is slightly sticky or you need to check freeplay in the cable. The trick with the throttle-stop screw could be down to:

1. The enrichment/choke not working properly - check ALL airways etc are clear.

2. Heavy contamination with oil weakening the mxture - does the bike appear to be using oil?

I am not surprised that he spark plug is carbon fouled if you are having the screw in the throttle-stop screw, this will enrichen the mixture, plug colours can only really be checked after 'normal' running.

Compression test worth doing - also have you checked valve and ignition timing?

Good luck

[sr125shell]

Thanks for the reply Fosdyke, I`ve not had the bike long & it`s basically been a non-runner - literally done about 2 miles!

I checked the operation of the throttle slide within the carb & it appears fine & snaps back nicely when releasing the throttle, doesn`t raise the throttle slide if you turn the handlebars which someone recommended I check.

I actually got my hands on a spare carb & it behaves exactly the same so I reckon the problem lies elsewhere? . It`s hard to tell the exact colour of the smoke, I`d say it was white/grey & it`s it consistent rather than big puffs.

I`ll do a compression test asap, the tester I bought didn`t have a correct sized adaptor which I`ve sent off for now.

many thanks for the help

Michelle

[jinxed]

Thanks for the reply Fosdyke, I`ve not had the bike long & it`s basically been a non-runner - literally done about 2 miles!

I checked the operation of the throttle slide within the carb & it appears fine & snaps back nicely when releasing the throttle, doesn`t raise the throttle slide if you turn the handlebars which someone recommended I check.

I actually got my hands on a spare carb & it behaves exactly the same so I reckon the problem lies elsewhere? . It`s hard to tell the exact colour of the smoke, I`d say it was white/grey & it`s it consistent rather than big puffs.

I`ll do a compression test asap, the tester I bought didn`t have a correct sized adaptor which I`ve sent off for now.

many thanks for the help

Michelle

Have all your tests been with the airfilter connected? Try it without the air filter & check the state of the air filter again. (There's a crankcase breather pipe connected to the air box on this model? Is it particularly wet with oil? I think my valve wasn't closing properly, before it broke, and this was causing oil to be pumped out into the air box.)

Are the carb rubbers in a good state? (Not split or damaged; shouldn't be on a 2003 model!) Also, check that the timing marks on the flywheel and camshaft gear are aligned as expected. (I managed to get mine offset once; it ran, poorly, and you could hear the engine through the carb/air-box; sounded great!)

I doubt the throttle stop screw will change the mixture; doesn't it just alter the position of the slider, thereby changing the idle speed? If the mixture looks too rich, re-check the mixture screw; try adjusting it whilst the engine is running & see if you can get it to behave better.

Have you actually ridden it? Does it pull like it should?

If you've bought this as a complete unknown, you should probably give everything the once over: Camshaft timing; valve clearances; compression; spark plug type.

Where'd you get your compression tester, BTW? Anyone got a PDF manual for the SR125?

[sr125shell]

Have all your tests been with the airfilter connected? Try it without the air filter & check the state of the air filter again. (There's a crankcase breather pipe connected to the air box on this model? Is it particularly wet with oil? I think my valve wasn't closing properly, before it broke, and this was causing oil to be pumped out into the air box.)

Are the carb rubbers in a good state? (Not split or damaged; shouldn't be on a 2003 model!) Also, check that the timing marks on the flywheel and camshaft gear are aligned as expected. (I managed to get mine offset once; it ran, poorly, and you could hear the engine through the carb/air-box; sounded great!)

I doubt the throttle stop screw will change the mixture; doesn't it just alter the position of the slider, thereby changing the idle speed? If the mixture looks too rich, re-check the mixture screw; try adjusting it whilst the engine is running & see if you can get it to behave better.

Have you actually ridden it? Does it pull like it should?

If you've bought this as a complete unknown, you should probably give everything the once over: Camshaft timing; valve clearances; compression; spark plug type.

Where'd you get your compression tester, BTW? Anyone got a PDF manual for the SR125?

Thanks Jinxed - feel I should have your username

I will check everything asap that you mentioned although I did check with/without air filter & it made no difference at all, rubbers look fine. I`ll have more time to get stuck in at the weekend & will report everything I do/find.

I got my compression tester here; http://www.amazon.co.uk/Draper-37442-Compr...8164&sr=8-1

In the description it says it goes upto 30 psi - that should read 300.

I also needed the adaptor here; http://www.amazon.co.uk/Draper-YDCT1-COMPR...8164&sr=8-3

the adaptor will come via royal mail who are now on strike for the week

I have the pdf user manual for the sr125 - what email address do you want me to send it to?

cheers

Michelle

[jinxed]

Thanks Jinxed - feel I should have your username

I will check everything asap that you mentioned although I did check with/without air filter & it made no difference at all, rubbers look fine. I`ll have more time to get stuck in at the weekend & will report everything I do/find.

I got my compression tester here; http://www.amazon.co.uk/Draper-37442-Compr...8164&sr=8-1

In the description it says it goes upto 30 psi - that should read 300.

I also needed the adaptor here; http://www.amazon.co.uk/Draper-YDCT1-COMPR...8164&sr=8-3

the adaptor will come via royal mail who are now on strike for the week

I have the pdf user manual for the sr125 - what email address do you want me to send it to?

cheers

Michelle

Trust me; my user name is VERY apt if you ever get to see my SR! (And the box of broken bits that I am slowly accumulating.) I must get a picture of it up .... or what's left of it.

A compression tester should be on my workshop "must haves" list; along with a valve spring compressor.

I just finished putting an engine back together that I bought 2nd hand. Previous owner said it just stopped working; he'd taken the top end of & then put it back together and given up. I found that one of the valve adjusters had lost it's lock nut and the valve probably wasn't opening any more; I adjusted the valve and then the engine jammed part way round; camshaft timing was WAY off! Better safe than sorry, I took the head off to check for other damage. Found some parts missing; found the valve locknut after shaking the head about. (Locknut is now oval shaped.) This engine should be going in my SR soon; the original engine is shot, especially after I let it run out of oil recently.

Moral to this story? Don't buy a bike off me and check all the basics on the engine, I guess.

Thanks for the offer of the manual; I probably need to find the earlier manual too as I have an '86 bike and a '96 engine and need the two to co-habit. The search continues!

(You're probably a bit far away for me to drop in & give you the benefit of my limited SR knowledge.)

[Virago535]

Hi, my SR125 is giving me a headache. It won`t start correctly.

Basically the only way I can get it to start without throttle is to fully turn the throttle stop screw adjuster all the way in (basically the same as giving throttle) but this leads to crazily high idle speeds & once I adjust the idle speed back to normal if I try to use the throttle it hangs at high revs for several seconds before attempting to idle properly again & the engine will eventually die + not restart without going through the whole procedure again. The choke doesn`t help starting at all.

Noticed white smoke from the exhaust also, but could just be condensation?

Carbs have been cleaned & floats, fuel mixture screw etc checked & set at correct heights.

Spark plug was carbon coated when I checked it (running rich?)

Air & fuel filters checked.

Throttle cable checked.

Any help with this is greatly appreciated

Thanks

Michelle

Hi - Did you ever discover the problem as mine has developed the exact same fault. I am beginning to suspect the CDI unit however i dont have a manual as yet so i am unsure of how much this unit actually controls. Any help would be appreciated.

Angela

[sr125shell]

Hi - Did you ever discover the problem as mine has developed the exact same fault. I am beginning to suspect the CDI unit however i dont have a manual as yet so i am unsure of how much this unit actually controls. Any help would be appreciated.

Angela

HI, my cam chain tensioner blade was basically ripped in two somehow + the throttle cable looked a little damaged- I`m guessing the previous owner had over-tightened it (they are automatically tensioned from 1997 I believe so don`t need adjustment). I did all the work myself & spent quite a few quid on tools such as flywheel remover, impact wrench, strap wrench, impact sockets, torque wrench, good spanner set & a Haynes manual.

It took me quite a while as it was my first attempt at taking an engine apart, cost a bit in parts (£26 cam tensioner blade, about £20 in gaskets for cylinder head, barrel & generator + £16 for a throttle cable) but as the garage wanted £150 just to fit the blade I thought sod that! plus I cleaned up piston & rings etc & everything else I had access to. I very carefully put it all back together.

Bike is running fine at the moment so I must`ve done something right!

Get yourself a Haynes manual for starters Angela

[Virago535]

HI, my cam chain tensioner blade was basically ripped in two somehow + the throttle cable looked a little damaged- I`m guessing the previous owner had over-tightened it (they are automatically tensioned from 1997 I believe so don`t need adjustment). I did all the work myself & spent quite a few quid on tools such as flywheel remover, impact wrench, strap wrench, impact sockets, torque wrench, good spanner set & a Haynes manual.

It took me quite a while as it was my first attempt at taking an engine apart, cost a bit in parts (£26 cam tensioner blade, about £20 in gaskets for cylinder head, barrel & generator + £16 for a throttle cable) but as the garage wanted £150 just to fit the blade I thought sod that! plus I cleaned up piston & rings etc & everything else I had access to. I very carefully put it all back together.

Bike is running fine at the moment so I must`ve done something right!

Get yourself a Haynes manual for starters Angela

Thanks for that - at least it is something to work on. Much appreciated

[jinxed]

HI, my cam chain tensioner blade was basically ripped in two somehow + the throttle cable looked a little damaged- I`m guessing the previous owner had over-tightened it (they are automatically tensioned from 1997 I believe so don`t need adjustment). I did all the work myself & spent quite a few quid on tools such as flywheel remover, impact wrench, strap wrench, impact sockets, torque wrench, good spanner set & a Haynes manual.

It took me quite a while as it was my first attempt at taking an engine apart, cost a bit in parts (£26 cam tensioner blade, about £20 in gaskets for cylinder head, barrel & generator + £16 for a throttle cable) but as the garage wanted £150 just to fit the blade I thought sod that! plus I cleaned up piston & rings etc & everything else I had access to. I very carefully put it all back together.

Bike is running fine at the moment so I must`ve done something right!

Get yourself a Haynes manual for starters Angela

Ooh! Can I ask where you got your flywheel remover from and what size it is?

Way to go fixing it yourself!! I hope it lasts longer than one of my repairs!

[jinxed]

Ooh! Can I ask where you got your flywheel remover from and what size it is?

Way to go fixing it yourself!! I hope it lasts longer than one of my repairs!

Ahh! (0h, ahh?) Just seen your other post. I had measured mine at 16mm, but good to hear I measured it right. I think the rear axle from another of the bikes will fit, but I don't want to mangle the axle.

[sr125shell]

Ahh! (0h, ahh?) Just seen your other post. I had measured mine at 16mm, but good to hear I measured it right. I think the rear axle from another of the bikes will fit, but I don't want to mangle the axle.

I got a 6-in-1 puller from Ebay for about £15 - asked the guy first though whether it had 16mm or not - worked no problem! Plus I have the other 5 sizes if needed in the future

[sr125shell]

I got a 6-in-1 puller from Ebay for about £15 - asked the guy first though whether it had 16mm or not - worked no problem! Plus I have the other 5 sizes if needed in the future

was exactly like this one on ebay - item number 250186074942 - hope it helps

[jinxed]

was exactly like this one on ebay - item number 250186074942 - hope it helps

Thanks! I'll take a look at that one. For some reason, I thought that the tensioner could be replaced once the head & barrel was removed; why remove the flywheel?

[sr125shell]

Thanks! I'll take a look at that one. For some reason, I thought that the tensioner could be replaced once the head & barrel was removed; why remove the flywheel?

The tensioner blade is behind the flywheel - the 2 bolts that retain it - that`s what had ripped in two & needed replacing.

[jinxed]

I ordered one of those pullers & it turned up really promptly; useful piece of kit. A few hours later and I had swopped the engines over on the SR. Thanks for the shopping tip!

[sr125shell]

I ordered one of those pullers & it turned up really promptly; useful piece of kit. A few hours later and I had swopped the engines over on the SR. Thanks for the shopping tip!

No Problem!