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Yamaha TTR125 Revisiting


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Hi Guys,

A small update from last time couple of months on the TTR125. And a couple queries!

Cleaned and rebuilt the carburettor, new oil, new petrol, cleaned the air filter, new spark plug.. Finally got her running!

A Matter of days after it was running the electric starter stopped working, the clicking with full battery charge all the that I needed.

So Im about 75% certain the starter has packed in. Anyone know any methods for testing these things?

Anyway I put it to a "mechanic" I use that term loosely.. who let the bike rott in his garage for 6 weeks which did not help matters.

So here I am 2 days ago I got the bike back and have decided to pour many hours of work into solving the problem.

With the carb rebuilt, floats set to allow enough fuel into the bowl, all completely clean, new fuel, new oil, no electric start now,

Ive removed the air filter to just let air flow in,

I am trying to kick this M*therf*c*er over and will it start will it heck!

My question is I have been scanning the internet and I think it may be the valves? Does anyone have any experience with checking them?

I can only see it being an internal problem especially if the carburettor has been completely rebuilt, kicking the engine you just get the exhaust rumbling away

but no ignition.

Any help from anyone or hints on things I have missed is much appreciated!

Cheers Again

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  • Moderator

The easiest thing it to tackle one thing at a time.

If no one has messed with the valves, then they may be out but I doubt that this is the problem.

1). Check you have got a spark - Take out the plug, hold it against a good earth (the engine head?) and see if it sparks when you kick the bike over. be careful and hole the plug with an insulated pair of pliers. Take not of the spark colour. Make sure the plug is clean and is gapped correctly.

2) if you get a spark that is blue and "fat", pour a little petrol into the plug hole, replace the plug and HT cable and kick the bike over again. What happens?

3) After you have tried to start the bike, if it is still not starting, take out the plug, clean and dry it. Return the plug into the hole and try and start the bike again. After a few kicks remove the plug and see what it looks like. Is it wet? smell it, does it smell of fresh petrol?

If you don't get a spark when you do number 1 then the issue is electrical and so you need to start checking that. A new plug and plug cap never hurt.

Do this and report the findings back.

As for the electric start, clean all of the connections from the battery, past the relay to the starter before you start to look to replace this. You can use a thick cable from the +ve of the battery directly to the positive side of the starter motor to test if the starter motor spins. Be careful here, a thin cable will get very hot and may hurt.

You must have some degree of mechanical and electrical knowledge to do these tests safely. You need to decide if you can carry these out safely.

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Cheers for the reply DirtyDT,

Heres what Ive got,

1) There was a spark when I kicked the bike over, the colour of it was white and it was just a small one definately not "fat".

2) Just for the sake of findings I carried out number 2, there was just the same the exhaust rumbling away but no start.

3) I did as you said for three took it out clean and dried it then replaced it kicked the bike over a few more times and the plug was clean when I removed it,

no oil, no petrol, just dry.

Ive taken some videos of kicking the bike over, the spark plug earthing and the actual noise from the electric start (but that can wait Im only really worried about actually getting the thing to run when Im kicking it) which are just uploading to YouTube so ill post the 3 links in here when theyre up.

Again thanks for your help!

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OK.

The spark looks OK but worrying that the plug is dry.

Take the plug out, push the kickstart. Can you hear the piston moving in the engine? Put your thumb over the plug hole and push the kickstart. Can you feel a fair amount of pressure when you use the kickstart?

Put the fuel tap onto off, take the fuel pipe off the carb and, using a container to catch it, when you turn the fuel tap to reserve does fuel come out of the pipe? Reconnect the pipe and put the tap onto reserve.

Put the plug back in - cleaned if required. Take off the petrol tank filler cap and leave off. Undo the airbox air pipe at the rear of the carb, with the choke off and the throttle fully open, spray a liberal amount of WD40 into the rear of the carb. Try and start the bike.

Let me know what each result is.

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We have progress!

The piston is definitely moving, I managed to get the engine running but its not idling, so I was continuously revving it.

As for the pressure when I use kickstart Im not too convinced I can near enough hold my finger on it!

Fuel did come out of the tap whilst it was in reserve, I never had any WD40 but I used some Easy Start spray.

Before the engine started the first time, there was a series of pops when I was kicking it? Im not sure what that is?

All in all the engine started working which is absolutely fantastic! although Im not sure its too healthy, when I held the throttle at a set position the revs weren't consistent cutting off

and came back continuously, it heated up really quickly as well.

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The next thing I would do is take the carb off, strip and clean it. I would also drain the fuel and put new petrol in it.

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Before messing with the jetting put the airfilter back.

It should help starting and the idle too.

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Ok Gentlemen,

I have taken heed of your information and more ground has been gained!

I took out the carb and cleaned it again, I already had new fuel in the system, replaced the air filter and blow and behold it would not start!

BUT from utterly nothing, I kicked it one last time and my hand slipped and opened the throttle about 10mm and it started straight away!

I fiddled with the idling screw and now not only does it start but it sits there purring away to its hearts content! (This is straight from a kickstart it goes into idling)

Its now idling but sometimes when I open the throttle it cuts out and other times it actually revs away, so I'm not particularly sure what this means?

I am very keen on taking it out for a ride but I have noticed the front wheel is not perpendicular to the handlebars, wondering if anyone could give me any advice on adjusting it?

Absolutely delighted though! Cheers for your help! :D

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Still sounds like a fuelling issue. Is the air filter new? Could be the choke and did you rebuild the carb and re set everything like the float height? Check the carb to air filter tube for splits. As for the wheel and handlebar issue, you need to determine what is out, the wheel or the bars. Bars can bend if the bike has been dropped and wheels/forks can twist. The latter can make it interesting when braking as it will "kick up" when you apply the brakes. Is one bar higher than the other or are the bars not straight when the wheel is pointing forward?

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Its not a new filter, when I cleaned it it was starting to tear but I didnt think it would disrupt the flow to much?

Would the choke have to be pulled for this to happen?

Yeah, I took apart the carb prior to this about 3/4 years ago when I hadnt a clue about bikes and never took note of the settings!

As of recently I have changed the idling screw, the float height had to be changed too because there wasnt enough fuel going into the carb.

Everything else is more or less set between 1-2 screw turns out.

The bars aren't straight when the wheel points forward, which sounds like by what your saying its twisted probably from sitting for the past 4 years!

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I just had it running in the garage there and I noted a few things with it running:

- The Spark Plug was Black when I removed it today this is only from kickstarting twice, Im not sure if this is normal?

- Also you were talking about the choke, the actual choke lead, the connection between the carb and the head of the lead is very worn, to the point where it is difficult to actually seat it within the carburettor. How badly does this affect the carbs performance?

Cheers Again!

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Dodgy air filter, Choke issue and a black plug = running to rich. Change the filter and sort the choke out.

Bar wise - you need to check if the bars are symmetrical. The bars could be bent or the forks may be out. You may get some joy by loosening the bolts that hold the forks to the yolks and then re-tightening but be careful that the bike doesn't drop down the forks. Chances are the forks are bent and will need replacing.

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Alright DirtyDT,

Ive ordered a new air filter and Im enquiring about a new choke lead on eBay. Until I receive them I probably wont be on here for a couple of days!

I thought I might try to tune the carburettor since I dont have any idea of the screw turns/ adjustment I was going to ask you if these bikes really take a lot of detail to work?

I mean the engine is running how much more do you need? Is it right down to specific detail on the pilot jet/air screw and idle screw or if they were roughly att he right setting would it not hopefully work!?

Anyway Cheers for your help!

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