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Main Jet Size And Bogging Stuttering 87Tzr

#1 User is offline   klimtachakka 

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Posted 11 March 2017 - 04:36 PM

HI!
Recently bought an old tzr 125 1987, steel frame and rear drum brake.
Got ut running somewhat now:
It tops out at about 60Mph/100kmh, but it bogs down on WOT. I can nurse it with half throttle and make it Rev to around 11K.
But at wot it just stutters at around 7K.
Ypvs valve is connected and working. (fully open with engine off and cycles when switching the ignition. I have also tried with ypvs disconnected but the same problem with 7K rpm at wot.)

Tried switching plug. No difference.
Plug looks descent at idle but oily black at wot.
It seems like it's running rich at wot and misfires. But it should not be rich if it is a standard main jet size?
Needle clip is at the most top (lean?)

Main jet is a 240, is this standard?
I also have a dtr125 and that has a 240 and runs well with that.

Help appreciateted.

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#2 User is offline   klimtachakka 

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Posted 12 March 2017 - 06:13 PM

plug at idle, looks good to me (?) (it idles fine and pulls fine when not rolling the throttle all the way back...
Attached File  idle.jpg (89.25K)
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plug at WOT (misfires and wont rev past ~7-8000 rpm) looks way to rich? Or am I reading this wrong?
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A picture of the beast. Damn fun to ride this thing.
Attached File  tzr.jpg (187.32K)
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#3 User is offline   tzrtony 

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Posted 12 March 2017 - 07:15 PM

Hi, and welcome to the forum,

I cannot remember off the top of my head what the stock size should be, but a few things can effect what you are saying.


Before i go ahead and trawl through my notes on the jetting, a few things can effect your mixture.


Filter -
Are you running a stock filter?
If yes, - is it blocked/dirty
If no, go back to a stock filter, as these bikes do not like K&N style filters.

Condition of the Inlet Rubbers -
Are there any cracks, or slits in the rubber, as this will effect the fuelling drastically

Condition of the reeds -
what are they like? when were they last changed? what sort is in there now?

What Exhaust are you running?

Are you running premix or are you using the stock 2t tank?

Whats the compression like?

are you running an external fuel filter?
If yes, ditch it now. :) lol

The plug is not as bad as i initially thought,
If everything else is normal (the list i posted above) then the jet size could do with coming down.

#4 User is offline   klimtachakka 

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Posted 12 March 2017 - 07:40 PM

View Posttzrtony, on 12 March 2017 - 07:15 PM, said:

Hi, and welcome to the forum,

I cannot remember off the top of my head what the stock size should be, but a few things can effect what you are saying.


Before i go ahead and trawl through my notes on the jetting, a few things can effect your mixture.


Filter -
Are you running a stock filter?
If yes, - is it blocked/dirty
If no, go back to a stock filter, as these bikes do not like K&N style filters.

Condition of the Inlet Rubbers -
Are there any cracks, or slits in the rubber, as this will effect the fuelling drastically

Condition of the reeds -
what are they like? when were they last changed? what sort is in there now?

What Exhaust are you running?

Are you running premix or are you using the stock 2t tank?

Whats the compression like?

are you running an external fuel filter?
If yes, ditch it now. :) lol

The plug is not as bad as i initially thought,
If everything else is normal (the list i posted above) then the jet size could do with coming down.



Filter -
stock airbox, brand new filter.

Condition of the Inlet Rubbers -
Inlet rubbers looks okay, but have only glanced at them when the carb was out for cleaning.

Condition of the reeds -
No idea, stock I guess..? They looked white/yellow if I remember correctly.

What Exhaust are you running?
Stock, and it is "de-oiled", pictures below.

Are you running premix or are you using the stock 2t tank?
stock 2t tank and pump is hooked up, but I don't think it works because now white smoke when pulling on the pump wire. So premix 50:1

Whats the compression like?
Don't know, I don't have a compression tester, but it starts very easy on first kick. Feels similar in resistance to the DTR. Maybe slightly easier pull on the TZR.

are you running an external fuel filter?
no, straight hose to the carb.


I looked through the haynes manual, and that states a stock main jet to be 180 haynes manual
But I have read everything from 180 - 240 on the net, so not sure what it shold be. And the DTR I have has a 240 and runs good, no performance mods on that either.


De-oiling:
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Attached File  123a91fa-40a1-49ae-a3cf-08b40dd7cc46.jpg (109.01K)
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#5 User is offline   tzrtony 

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Posted 13 March 2017 - 04:17 PM

yeah a 180 on the TZR sounds about right,

240 on the DT is correct, as the DT uses a longer stroke, they may look the same engine, but they are not.

drop your main down to 180, (190 if you intend to run premix permanently)

but the 2t pumps are very reliable, unless they are not bled properly after being left to run dry. There is a bled nipple on the top of the housing that needs undoing, and aloow the oil to seep out a little :)

#6 User is offline   klimtachakka 

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Posted 13 March 2017 - 07:59 PM

Thanks for you answers.
Does look like the right one:
main jet ?

Also, does anyone know why the hell someone would fit it with a 240 jet when it clearly does not run at all above 50% throttle with it ??

#7 User is offline   tzrtony 

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Posted 16 March 2017 - 07:14 PM

yeah, looks about right fella.

Just a word of advice though,
For little items that have a massive effect on how the bike runs, unless you can actually trust 100% the quality of the item, it is always better to go main stealer (dealer) route. as they will be genuine quality :)


Hope your back to WOT pretty soon.


Tony.

#8 User is offline   Cagiva4ever 

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Posted 23 March 2017 - 11:59 AM

have you checked for "Crank wiggle" vertically ? Yamaha engines are Notorius for Crank to wearout for Bearing fittment onto the crank. because the fittment isnt tight, and instead is Typical Japanise...

if the Crank wobbles (Wiggle the FlyWheel vertically) it lets Crank main seal to BlowBy-AirLeak, which intereferences into Mixture.

^this effect especially appears/shows up on 1st PowerBand , as a splutter hesitation, wont Rev pass it depending of a SetUp etc engine specs.

ive mentioned many times before, that industrial tolerance/alignemnt for such oilseal is 0,1mm ,before is start to leak by-pass. a Wobbly crank/bearing fittment causes same effect, that also has effect from centrifugal forces and rpm how it behaves, makes a figure "sun flower" so to speak, Due to it can appear intermittent...........also Due the stroke going into TDC, versus BDC.......

#9 User is offline   klimtachakka 

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Posted 29 March 2017 - 02:46 PM

So I got the new Jet. It run's better with it, but not as good as it should. It will rev out in first, but in higher gears it seems like the problem with 7-8krpm still exist.
At first I had the needle in the middle position. Did not feel a change, then changed it to the top (most lean) and that made it better. But still bogging down under load in the 7-8k ..

Did not do a plugchop on the last run. Will do that again at WOT. Could it be a worn needle and the thing that meets the needle causing it to run rich still?

Thanks, will check flywheel/crank wiggle.

#10 User is offline   tzrtony 

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Posted 29 March 2017 - 07:52 PM

if everything is ok mechanically,

then you may still need to drop a size on the jet again.

its always a bit hit or miss when tuning, so sometimes your adjustments might not quite be enough.

Hence why alot of people take them to the garage. Garages tend to have quite a few jets to hand, and can swap them out in minutes, rather than waiting for good ol mr postman. :)

You are heading in the right direction, so check mechanicals, swap the needle out for a new one, then drop the jet size again,.


Remember 180 is UK spec, your in sweden, so the atmospheric conditions are completly different there, it also depends on humidity, altitude, and temperature. http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/thumbsup.png so a slight variation is expected.

you can always read up on spankys tuning guide (found in one of my posts, in the manuals section for the TZR) That alone should give you everything you may need to know about tuning a 2 stroke. Even if you think you know everything, it still makes a damb good read :)

#11 User is offline   klimtachakka 

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Posted 04 April 2017 - 06:55 PM

Got some time in the garage today. Had a lookaround and found a pitbike foam filter and thought, why not.. if it's rich at the moment it should be leaner with the foam filter.
Said and done, removed the airbox, popped the foam on, fired her up and let it idle for a couple of minutes.
Holy sh*t, it pulls like a raped ape now ( for what it is, but still) . No hesitation and no bogging, might be lacking a little in the bottom but I can live with that.
Not bad for a 30 year old 124cc beaten up old two stroke with 60.000k's on the clocks. Got it up to 130km/h but then I remembered I had a an mx lid and a t-shirt on. So I eased it down.
I'm a happy camper now. Thanks for all the help and tips.
Will post a picture later when it's assembled with all the fairings and doo-dads.

Oh, almost forgot, the induction roar it makes now, almost makes the hair on you neck stand up.

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This post has been edited by klimtachakka: 04 April 2017 - 06:56 PM


#12 User is offline   tzrtony 

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Posted 05 April 2017 - 04:14 PM

Nice, glad your almost there with her.

These bikes do pull really well when they are tuned properly :) lol.

But, the sluggishness your now experiencing, is because you have a static power valve,

with the static power valve, to give one area a boost, you have to take from another. Nothing is free :)

If you were to put a servo on there however, thats where the rules change, and you get your cake and you can eat it too http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/thumbup.gif

#13 User is offline   klimtachakka 

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Posted 06 April 2017 - 11:05 AM

View Posttzrtony, on 05 April 2017 - 04:14 PM, said:

Nice, glad your almost there with her.

These bikes do pull really well when they are tuned properly :) lol.

But, the sluggishness your now experiencing, is because you have a static power valve,

with the static power valve, to give one area a boost, you have to take from another. Nothing is free :)

If you were to put a servo on there however, thats where the rules change, and you get your cake and you can eat it too http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/thumbup.gif


It does actually have a servo and I think it is working as it should. I can hear the cycling when turning the ignition and the hole lines up in the slot when opening the pv-cover.
If I unplug the servo controller it runs like crap.

#14 User is offline   tzrtony 

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Posted 06 April 2017 - 05:57 PM

ahh, didnt realise you had the PV fitter http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/blushing.gif

butyeah, they tend to run like a bag of poo when you disconnect it. http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/laugh.gif

it could be, that you are very close, but not close enough to have a good smooth power delivery.

If you get time check out spanks 2t tuning guide. go through that to the letter, and you WILL have a well tuned carb in no time at all http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/thumbsup.png

it does take some time to get there, but when oyu do, by god is it worth it

#15 User is offline   klimtachakka 

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Posted 09 April 2017 - 07:05 PM

View Posttzrtony, on 06 April 2017 - 05:57 PM, said:

ahh, didnt realise you had the PV fitter http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/blushing.gif

butyeah, they tend to run like a bag of poo when you disconnect it. http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/laugh.gif

it could be, that you are very close, but not close enough to have a good smooth power delivery.

If you get time check out spanks 2t tuning guide. go through that to the letter, and you WILL have a well tuned carb in no time at all http://www.125ccsportsbikes.com/forums/public/style_emoticons/default/thumbsup.png

it does take some time to get there, but when oyu do, by god is it worth it


Not trying to be an idiot here, but.. where do I find this spanks tuning guide? I tried using the search but that didn't go so well....

#16 User is offline   tzrtony 

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Posted 09 April 2017 - 09:31 PM

CLICK ME :) <------ Spankeys tuning guide :)

#17 User is offline   klimtachakka 

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Posted 17 May 2017 - 06:55 PM

As she stands now. Last ride was about 45km. It's a really sweet machine to just cruise around on. Thanks for all the help.

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