A forum for owners of Yamaha TTR250 trail and enduro bikes!

TheWizardofOdds · Senior Member

Engine stalling in first/low speed

TT-R250M · Super Guru

Check your idle speed is correct. If it is, the first thing I would suggest is a good carb clean. The idle/pilot jet may be partially blocked. This thread should help- http://ttr250.activeboard.com/t55374798/rebuilding-a-ttr250-teikei-y30p-carburettor/

If that doesn't help, report back.

Jarrah

TheWizardofOdds · Senior Member

Thanks Jarrah. I think I'll look at the idle speed first and failing that get stuck in to the carb. Again.

TheWizardofOdds · Senior Member

Referring to the service manual for idle speed adjustment states that I need an inductive tachometer to check the idle speed. Ideally that would be ok but is it something you can do without?

When I spoke to a colleague about this he said I might need to adjust the air/fuel mixture on the carb by turning a screw. How is this done on the TTR and is it relevant to my problem?

I'm just checking before I get involved with removing the carburettor again.

TT-R250M · Super Guru

TheWizardofOdds wrote:
Referring to the service manual for idle speed adjustment states that I need an inductive tachometer to check the idle speed. Ideally that would be ok but is it something you can do without?

When I spoke to a colleague about this he said I might need to adjust the air/fuel mixture on the carb by turning a screw. How is this done on the TTR and is it relevant to my problem?

I'm just checking before I get involved with removing the carburettor again.

If it was screwed all the way in or about to drop out it may give you trouble. Otherwise I would say the pilot jet is partially blocked. To adjust the fuel metering screw, turn it in all the way (taking note of how many turns it is set at) and re-adjust to 1 1/2~ 2~1/2 turns out. Start the engine and rev the throttle up until 1/3 throttle. If it is sluggish or slow to pick up in revs, adjust the fuel screw until it seems right. The best setting is usually found when the engine idles the highest. Re-adjust throttle speed until the engine speed is around 1000rpm~1200rpm (that's how I like it set anyway). As long as it is idling without stalling and does not sound like it's revving it's tits off, it is good enough. smile

Jarrah

ttboof · Super Guru

sounds like a good carb clean and reset

mght pay to check the inlet manifold just incase the rubber has started to seperate .

TheWizardofOdds · Senior Member

Thanks for the replies.

I put a new pilot jet in a month or two back so that should be ok. I'll have a go at adjusting the idle speed and see what happens. Failing that, it indeed seems like I'm going to have to get the carb out and lick it clean or something.

I took the bike out yesterday being such a nice day and had to use full choke for a bit then eased it back in resulting in poor performance. As soon as I came back down to first gear, again clutch in, the bike just cut out and the back wheel locked. So this thing is going nowhere until I get it sorted.

ttboof · Super Guru

TheWizardofOdds wrote:
Thanks for the replies.

I put a new pilot jet in a month or two back so that should be ok. I'll have a go at adjusting the idle speed and see what happens. Failing that, it indeed seems like I'm going to have to get the carb out and lick it clean or something.

I took the bike out yesterday being such a nice day and had to use full choke for a bit then eased it back in resulting in poor performance. As soon as I came back down to first gear, again clutch in, the bike just cut out and the back wheel locked. So this thing is going nowhere until I get it sorted.

the need for extra choke to make it run , indicates its running lean , before you pull the carby off again get it running and spray something like WD40 around the inlet manifold rubber if its leaking the engine speed will change as you spray it . check B with the engine running wiggle the carb gently and see if it causes the engine speed to change . only suggesting this based on you have done all the usual carby stuff which should have fixed the problem if all else is good .

another last resort could be a problem with the inlet valves /clearance , unlike likely but possible ( as was the case on a mates XR I fixed a couple of days ago ) just clarifying the Honda connection I did the whole job at night and out of sight I'm not a fan of the dark pink brand .

Bugeye_bob · Veteran Member

TheWizardofOdds wrote:
Thanks for the replies.

I put a new pilot jet in a month or two back so that should be ok. I'll have a go at adjusting the idle speed and see what happens. Failing that, it indeed seems like I'm going to have to get the carb out and lick it clean or something.

I took the bike out yesterday being such a nice day and had to use full choke for a bit then eased it back in resulting in poor performance. As soon as I came back down to first gear, again clutch in, the bike just cut out and the back wheel locked. So this thing is going nowhere until I get it sorted.

with the clutch lever pulled in the rear wheel shouldn`t lock up, you should be able to free wheel.

TheWizardofOdds · Senior Member

ttboof wrote:
TheWizardofOdds wrote:
Thanks for the replies.

I put a new pilot jet in a month or two back so that should be ok. I'll have a go at adjusting the idle speed and see what happens. Failing that, it indeed seems like I'm going to have to get the carb out and lick it clean or something.

I took the bike out yesterday being such a nice day and had to use full choke for a bit then eased it back in resulting in poor performance. As soon as I came back down to first gear, again clutch in, the bike just cut out and the back wheel locked. So this thing is going nowhere until I get it sorted.

the need for extra choke to make it run , indicates its running lean , before you pull the carby off again get it running and spray something like WD40 around the inlet manifold rubber if its leaking the engine speed will change as you spray it . check B with the engine running wiggle the carb gently and see if it causes the engine speed to change . only suggesting this based on you have done all the usual carby stuff which should have fixed the problem if all else is good .

another last resort could be a problem with the inlet valves /clearance , unlike likely but possible ( as was the case on a mates XR I fixed a couple of days ago ) just clarifying the Honda connection I did the whole job at night and out of sight I'm not a fan of the dark pink brand .

I'll give it a go. I haven't the faintest idea what's the matter. I've a feeling that carb's coming out though.

TheWizardofOdds · Senior Member

Bugeye_bob wrote:
TheWizardofOdds wrote:
Thanks for the replies.

I put a new pilot jet in a month or two back so that should be ok. I'll have a go at adjusting the idle speed and see what happens. Failing that, it indeed seems like I'm going to have to get the carb out and lick it clean or something.

I took the bike out yesterday being such a nice day and had to use full choke for a bit then eased it back in resulting in poor performance. As soon as I came back down to first gear, again clutch in, the bike just cut out and the back wheel locked. So this thing is going nowhere until I get it sorted.

with the clutch lever pulled in the rear wheel shouldn`t lock up, you should be able to free wheel.

The wheel definitely locked. I'm sure the lever was in as I was at that point testing it to see if the engine would cut out. Strange.

Terrence R · Senior Member

Have you ever checked your clutch basket for notches? It could be stalling due to the friction plates not being able to spread open far enough. Just a thought.

TheWizardofOdds · Senior Member

Terrence R wrote:
Have you ever checked your clutch basket for notches? It could be stalling due to the friction plates not being able to spread open far enough. Just a thought.

Thanks, but that's lost on me. I'll try idle/carb first and then look into your suggestion. Gulp...

It will be Thursday before I can have a look and see what's what so thought I'd take this opportunity to ask some more questions.

As the bike won't idle without choke, will that affect my attempt at adjusting the idle rpm? I imagine the bike should be idling without for me to gauge/adjust it properly?

Before I take the carb out and replace everything I can and put it back in...

What is the likely culprit? I have a new pilot jet in so imagine it can't be that.

Could it be the accelerator pump is blocked or something? If the bike is running lean and fuel or air isn't getting through in the right quantity at low revs does it mean some other jet is blocked?

My plan is to follow Jarrah's rebuild thread on the carb and take it step by step, assuming the idle adjustment doesn't work.

In the service manual it says to drain the float bowl before removal. In order to check the acc pump I take it I don't drain the bowl? When I removed the carb the last time I lost loads of fuel somehow.

Bugeye_bob · Veteran Member

I take it you have ignored the last few messages then?
You cant help some folks.

TheWizardofOdds · Senior Member

Bugeye_bob wrote:
I take it you have ignored the last few messages then?
You cant help some folks.

I take it you have ignored my posts in reply then?

If you'd read them you would see I have acknowledged each one and will certainly get around to attending to each piece of advice as I have said.

Don't come on this thread accusing me of being ignorant. If you've nothing constructive to say, why say it?

Padowan · Senior Member

I've also had some fun trying to better understand the carb design as I have a similar problem on one of mine. As I understand it here's a list of some of the different jets, adjustments and orifices and what I believe they do - anyone feel free to correct if I'm spouting something incorrectly.

Main Jet - meters fuel at higher throttle opening - needs to be clear and the correct size or you'll run rich (too big)/lean (too small) - the adjustment you make on the main jet with the c-clips adjusts it's position relative to the needle.
Needle - sits inside main jet and increases the end orifice as the slide moves up and down.
Slide barrel - opens the throttle more to let more combustion air in.
Pilot Jet - meters fuel at low throttle position - needs to be clear and correctly sized. If restricted or blocked you'll need choke to idle.
Accelerator Pump - injects a squirt of fuel when opening the throttle - if blocked the engine will stall when opening the throttle as it'll go too lean due to the jets taking more time to react and pull in the required fuel amount.
Pilot jet air hole - directs air across the top of the the pilot jet which draws the fuel up from the bowl, if blocked/restricted the engine won't idle correctly without choke as the fuel isn't getting drawn up from the bowl.
Main jet air hole - same as above for the main jet, but I'm not sure where this air is exhausted, I assume through the jet/needle into the barrel.
Air-screw - I THINK this is the outlet from the pilot jet air hole, opening this more allows more air across the pilot jet and therefore richens the mixture slightly within the limits of the pilot jet size - I'm not sure however if it's just air, or an air/fuel mix that exits this hole..
Float - allows fuel into the bowl automatically as the level is depleted, if the float/valve is blocked the engine won't get fuel.

Bugeye_bob · Veteran Member

TheWizardofOdds wrote:
Bugeye_bob wrote:
I take it you have ignored the last few messages then?
You cant help some folks.
I take it you have ignored my posts in reply then?
If you'd read them you would see I have acknowledged each one and will certainly get around to attending to each piece of advice as I have said.
Don't come on this thread accusing me of being ignorant. If you've nothing constructive to say, why say it?

Because if your rear wheel is locking up with the clutch pulled in your looking in the wrong place for your problem,
It doesnt take a genius to work out that from what you have told us the clutch is dragging causing the bike to stall,
feck all to do with the carb if you use reason. . . . . .

TheWizardofOdds · Senior Member

Padowan wrote:
I've also had some fun trying to better understand the carb design as I have a similar problem on one of mine. As I understand it here's a list of some of the different jets, adjustments and orifices and what I believe they do - anyone feel free to correct if I'm spouting something incorrectly.

Main Jet - meters fuel at higher throttle opening - needs to be clear and the correct size or you'll run rich (too big)/lean (too small) - the adjustment you make on the main jet with the c-clips adjusts it's position relative to the needle.
Needle - sits inside main jet and increases the end orifice as the slide moves up and down.
Slide barrel - opens the throttle more to let more combustion air in.
Pilot Jet - meters fuel at low throttle position - needs to be clear and correctly sized. If restricted or blocked you'll need choke to idle.
Accelerator Pump - injects a squirt of fuel when opening the throttle - if blocked the engine will stall when opening the throttle as it'll go too lean due to the jets taking more time to react and pull in the required fuel amount.
Pilot jet air hole - directs air across the top of the the pilot jet which draws the fuel up from the bowl, if blocked/restricted the engine won't idle correctly without choke as the fuel isn't getting drawn up from the bowl.
Main jet air hole - same as above for the main jet, but I'm not sure where this air is exhausted, I assume through the jet/needle into the barrel.
Air-screw - I THINK this is the outlet from the pilot jet air hole, opening this more allows more air across the pilot jet and therefore richens the mixture slightly within the limits of the pilot jet size - I'm not sure however if it's just air, or an air/fuel mix that exits this hole..
Float - allows fuel into the bowl automatically as the level is depleted, if the float/valve is blocked the engine won't get fuel.

Thanks Padowan, nice breakdown!

At least I've got an idea what I'm looking at in the manuals etc. is now.

TheWizardofOdds · Senior Member

Finally got a chance today to have a go at sorting this out.

My plan was to replace the carb with another kindly supplied by Brian.

I adjusted the idle and it idled without choke after a bit. I then switched off the ignition and attached a tachometer to get a reading for the rpm. I then tried to restart the ignition and...nothing. It clicks and you can hear the solenoid? Is that right? The lights come on OK and everything seems fine but it just won't start?

I've got a feeling that the replacement carb will sort this as the engine is racing without any throttle at idle. I'll be damned if I know what's up with the starter though. Any suggestions?

chrisstdt · Senior Member

Either starter solinoid ,loose / dirty connection or sticky starter mine does the same sometimes just not got round to looking at it yet

TheWizardofOdds · Senior Member

chrisstdt wrote:
Either starter solinoid ,loose / dirty connection or sticky starter mine does the same sometimes just not got round to looking at it yet

OK. Is that reasonably easy to fix, do you know?

The bikes always started absolutely fine. It started no problem when I first fired it up. Weird.

chrisstdt · Senior Member

worst case is the starter ,theres a thread on here about rebuilding it ,its usualy down to sticky corroded brushes so fairly easy to fix

TheWizardofOdds · Senior Member

chrisstdt wrote:
worst case is the starter ,theres a thread on here about rebuilding it ,its usualy down to sticky corroded brushes so fairly easy to fix

Good stuff. I'll check it out thanks.

TTRfan · Super Guru

TheWizardofOdds wrote:
I then tried to restart the ignition and...nothing. It clicks and you can hear the solenoid? Is that right? The lights come on OK and everything seems fine but it just won't start?

I'll be damned if I know what's up with the starter though. Any suggestions?

Four main possibilities to explain your symptoms:

1. Bad connection - particularly the battery leads

2. Dirty connection on handlebar switch - or faulty switch

3. Solenoid

4. Sticking brushes

5. And the most obvious I guess - is the battery fully charged?

Do the easy things first is always my motto - make sure the battery is fully charged and the connections are on tight. It was a new battery so should be 100%

Sticking brushes can sometimes be diagnosed by keeping the starter button pressed whilst tapping the starter fairly hard with the blnt end of a biggish screwdriver - might need two people!

Brian

TheWizardofOdds · Senior Member

TTRfan wrote:
TheWizardofOdds wrote:
I then tried to restart the ignition and...nothing. It clicks and you can hear the solenoid? Is that right? The lights come on OK and everything seems fine but it just won't start?

I'll be damned if I know what's up with the starter though. Any suggestions?
Four main possibilities to explain your symptoms:
1. Bad connection - particularly the battery leads
2. Dirty connection on handlebar switch - or faulty switch
3. Solenoid
4. Sticking brushes
5. And the most obvious I guess - is the battery fully charged?

Do the easy things first is always my motto - make sure the battery is fully charged and the connections are on tight. It was a new battery so should be 100%
Sticking brushes can sometimes be diagnosed by keeping the starter button pressed whilst tapping the starter fairly hard with the blnt end of a biggish screwdriver - might need two people!
Brian

I left it last night Brian and was ready to start afresh this am. The bike started almost immediately on the second push of the start button. I went out last night and bought jump leads as I thought maybe the battery was flat. It seems that might have been the problem, the bike has had next to no use really for months. I took the bike out and it was OK. Its really racing though as I've raised the rpm so it wouldn't cut out on me. I've accepted defeat and taken it to a garage. The mechanic will only use the carb or parts if he has to Brian, I will get it back to you when its done. Thanks. I could have replaced it myself but thought I'd let the garage do it this once.

I'll be contacting you for parts soon though. I had the bike on choke left it for a minute came back and the battery cover and rhs panel were smoking! I stupidly had it on full choke. I'm a disaster. Lol.

-- Edited by TheWizardofOdds on Monday 24th of March 2014 02:52:07 PM

TheWizardofOdds · Senior Member

I got the bike back from the garage today. According to the mechanic the carb needle height needed adjusted. I can't remember if it was too low or high or what. Come to think of it, I don't know what a carb needle is either :)

The bike rides well and is a different animal. I'm glad I put it into the garage now. I'd never have known that would be the problem. Anyway its done now. Thanks for all the help everyone.