Help! Yamaha Mini Enduro Carb-running problem... Can't figure it out. Any advice appreciated! (Video of problem on YouTube).

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na...@my.net

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Feb 17, 2014, 6:44:48 PM2/17/14
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Hey Guys!

I semi-restored my JT1 (1972 Mini-Enduro 60) and after rebuilding the
carb the bike just doesn't want to run well. I'll nut-shell it in a
minute but here's a link to a video of the problem:
http://www.youtube.com/watch?v=6Jh2e68HF-s&feature=youtu.be

It will start but wants to die if I don't keep the gas on. Also, when
I do hit the gas the response isn't very crisp. The air screw is
adjusted per the manual and I have new jets (OEM). Also, there isn't
an adjustable float and the ball in the carb bowl tested good at
assembly. Using the choke does aid in starting but more often than
not I have to twist the throttle wide open to get it to go. (Like
when you crash and your 2stroke gets flooded). Also, I did get a bit
of gas out of the overflow today which really shouldn't happen. I
would think that this is a byproduct of a bad float in the bowl but it
did look okay when tested. (I guess I coulda missed something
wrong...).

Anyway, if ya have a little time please take a look at the youtube
video and listen... maybe someone with a better mechanical mind and
more experience can suggest the probable cause by hearing the
engine???

Thank you for any help you can give!!!

Scott



Mike S.

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Feb 18, 2014, 10:55:18 AM2/18/14
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Scott reports:

> I semi-restored my JT1 (1972 Mini-Enduro 60) and after rebuilding the
> carb the bike just doesn't want to run well. I'll nut-shell it in a
> minute but here's a link to a video of the problem:
> http://www.youtube.com/watch?v=6Jh2e68HF-s&feature=youtu.be

When it won't run without the choke on (which I saw in the video but
you don't really say in your post), that is a clear indication
of one of two things. The pilot jet is plugged (you have new jets so
unless there was crap in the tank or lines that isn't it) or you have
an air leak. Those rotary valve motors are hard on the seals
on the carb side and all two strokes have hardened seals when they
are 40 years old. You can try to confirm an air leak by
spritzing ether around the generator side (cover off) and maybe
you can do the same on the carb side but keeping it out of
the carb will be tough. Maybe use a WD-40 spray tube to get
down in there.

In any case, if there is a leak the ether will make the engine
speed up immediately.


Go fast. Take chances.
Mike S.



john

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Feb 18, 2014, 7:59:12 PM2/18/14
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like mike says
clogged jet or air leak


"Mike S." <nospa...@virtecnospamenterprises.com> wrote in message
news:ldvvp2$cn0$1...@dont-email.me...

Gozer

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Feb 19, 2014, 12:04:35 AM2/19/14
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On Tue, 18 Feb 2014 19:59:12 -0500, "john" <n...@diz.add> wrote:

Thanks Guys! I really appreciate the knowledgeable/experienced help!
I'm busting my tail at work at the moment but WILL get to it as soon
as I can. I'm stoked to have a good starting point(s) to
trouble-shoot first! I'll give an update as I go but since I have to
come up with the mortgage payment, it may not be tomorrow! But your
advice is MUCH appreciated!!!!!!!!
Thanks again!!! I appreciate the time!!!

Scott

Tiago

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Feb 19, 2014, 12:38:52 PM2/19/14
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On Monday, February 17, 2014 8:44:48 PM UTC-3, na...@my.net wrote:
> Hey Guys!

>
> Thank you for any help you can give!!!



You don't mention replacing needle and seat; with vibration, given enough time, one will "eat" into the other, making the hole larger and the needle thinner, which means more gas going into the engine. btdt...

However this causes a too rich symptom and while couldn't look at the video
(sorry), the more knowledgeable folks (lc john and Mike S) are suggesting you have a too lean condition... Is spark plug tip white, black or brown?

-- Tiago

na...@my.net

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Feb 19, 2014, 4:32:22 PM2/19/14
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Hey Taigo!

The bike actually ran fairly well before I dismantled it... It did
bog a bit but I'm sure that was from sitting with old gas for decades.
That's why I just went for the carb rebuild kit... When i had it
apart I installed a new piston and rings, and of course both head
gaskets. I think the needle and seat are fine (see above) and since I
installed a new spark plug I don't really have any color on it at all
yet! It did come out wet once, tho....

Thanks for the input, Bud!!!


ej2...@yahoo.com

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Apr 26, 2014, 1:02:23 PM4/26/14
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I recently picked up my dads old dirt bike and I want to fix it up so my kids could use it and keep it in the family. Im sure it hasn't ran since the early 80s. It has the JT1 serial number and the bike is light blue. I don't know if it has been painted ,but I would like to get some info on how to clean or remove the carb. and also why there is a separate oil reserved on the engine case? after searching all over the internet I was able to find out that its a 2stroke that mixes the gas and the oil by its self? Please correct me if im wrong. Thank you

Gozer

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May 4, 2014, 11:33:30 PM5/4/14
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>
>
>I recently picked up my dads old dirt bike and I want to fix it up so my kids could use it and keep it in the family. Im sure it hasn't ran since the early 80s. It has the JT1 serial number and the bike is light blue. I don't know if it has been painted ,but I would like to get some info on how to clean or remove the carb. and also why there is a separate oil reserved on the engine case? after searching all over the internet I was able to find out that its a 2stroke that mixes the gas and the oil by its self? Please correct me if im wrong. Thank you


If it's blue, that's not the original color.

Since the serial says JT1, take off the right engine case (3 or 4
screws). You will see the carb as well as the oil injector (when you
turn the throttle you will notice that the throttle cable has bees
split under the tank and pulls both the needle in the carb as well as
the pully to the left of the carb. the apperatis to the left is the
oil adding to the carb.

There is ONE screw that will release the carb and it is behind the
carb! The head of the screw is faced forward and is accessed by
taking a little round rubber deal off of the ver right of the case -
If U R looking at the carb, move right and look at the front of the
motor.. you'll see the round rubber deal that will pull out. take it
off and use a flat head screwdriver. The carb will just pull off.

Tear apart and clean.

ej2...@yahoo.com

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May 26, 2014, 7:15:14 PM5/26/14
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@ Gozer, thanks for the reply.
I took apart the carb, cleaned everything and put it back on.I put yamalube 2 stroke oil in the reserve and clean gas in the tank. I checked the spark plug and is currently gapped .024.as I try to kick start it I see smoke but nothing. is there a specific way the knob next to the choke is supposed to be? Or is the screws in the carb supposed to set a specific way? thank you

ej2...@yahoo.com

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May 26, 2014, 7:18:49 PM5/26/14
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On Monday, May 26, 2014 4:15:14 PM UTC-7, ej2...@yahoo.com wrote:
> @ Gozer, thanks for the reply.
>
> I took apart the carb, cleaned everything and put it back on.I put yamalube 2 stroke oil in the reserve and clean gas in the tank. I checked the spark plug and is currently gapped .024.as I try to kick start it I see smoke but nothing. is there a specific way the knob next to the choke is supposed to be? Or is the screws in the carb supposed to set a specific way? thank you

and after pulling apart the tank I noticed the bike was at one time yellow

Gozer

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May 27, 2014, 4:31:02 PM5/27/14
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On Mon, 26 May 2014 16:15:14 -0700 (PDT), ej2...@yahoo.com wrote:

>@ Gozer, thanks for the reply.
> I took apart the carb, cleaned everything and put it back on.I put yamalube 2 stroke oil in the reserve and clean gas in the tank. I checked the spark plug and is currently gapped .024.as I try to kick start it I see smoke but nothing. is there a specific way the knob next to the choke is supposed to be? Or is the screws in the carb supposed to set a specific way? thank you

Okay! Yellow means that it is a '72.

The knob next to the choke is the idle. There's no setting for it in
the manual although no matter where it's set, the bike would start -
you would just adjust the idle as it ran.

The only other adjust met on the carb would be the air screw. The
manual states that it should be set at 1 1/2 turns out although mine
was set at 1 1/4 and it ran well. In any case, both settings will
work so try at 1.5 and see how it runs. (The air screw is on the
front of the carb and a brass color - you can't miss it.)

If you're getting smoke then it has to be firing - gas and oil is
being burned. Timing is done with points and a magnito and the
electronics is under the tank (follow the spark plug cap upward and
you'll see the unit). If the points are bad it won't start - but in
that case you shouldn't be getting smoke, either. You can check to
see if the plug is good by unscrewing it from the head and putting it
back in the spark plug cap, then ground the metal lower part of the
plug to the unpainted part of the head (it'll just lay against
it...). then kick it over. You should be able to see the spark in
the gap of the plug (it's easier to see in a darker environment). But
again, if you're getting smoke then the plug must be firing...

The reality is that you need fuel, air and spark.

Anyway, good luck. It'd be nice if simply making sure the air screw
is 1.5 turns out wil fix this!

ej2...@yahoo.com

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May 27, 2014, 8:56:55 PM5/27/14
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okay, now the fuel seems to be mixed but dripping out of the exhaust where the muffler is connected. I maybe getting too much fuel? I checked for spark and its good.is there something im missing?

Gozer

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May 28, 2014, 7:28:05 PM5/28/14
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On Tue, 27 May 2014 17:56:55 -0700 (PDT), ej2...@yahoo.com wrote:

>okay, now the fuel seems to be mixed but dripping out of the exhaust where the muffler is connected. I maybe getting too much fuel? I checked for spark and its good.is there something im missing?

All 2 strokes have splooge coming out of the pipe but it's thick - not
gas like. The gas should be burning. What does the plug look like?
Is it wet after kicking it over? If it had been running before and it
was a very rich condition, the plug will be black (it should be a nice
tan color). It seems that the gas coming out of the pipe should be
coming out of the muffler end since there would be less resistence.
The muffler is held on by 1 screw - try taking it off and see if it is
completely clogged. The entrance is kinda small but rats and mice are
known to make homes in exhaust pipes. I had a buddy years ago who had
a bike in which some sort of animal made a mud nest in his pipe and
clogged it.

Remember you said that when you kicked it over, smoke came out of the
pipe? Was it actually smoke or the fuel mixture being pushed out? The
engine works on a vacuum and unburned gass/oil will get pushed thru
the system. If it isn't being burned then an actual gas mixture will
be building up in the pipe and dripping like you said. If that's
true, and you said you are getting spark, then there is probably
something very wrong with the jetting. Gas and spark, but not enough
air to ignite...

Did you have this bike running at one time? Or did you buy it not
running as a project?

Try doing this with both the choke on and off: Hold the throttle WIDE
OPEN, and kick it 20 times. See if it starts. To an extent, jets
regulate flow down, and a wide open throttle replicates a bike where
the carb kinda has no restrictions just as when you're riding it WFO!
(BTW - if you ever flood the bike, this is exactly how to start it).

I'm gone til next Monday so try the above - try the last thing,
holding it wide open and kicking, first... it's the easiest. Then
take off the pipe and see if it runs (it should start but won't have
much power). That'll tell you if the pipe is being restricted, but
also check out the pipw ehile it's off to make sure it isn't
blocked... When you kick it, is it smoke or unburned gas mix?

Of yea, one more thing: There is a float ball/barrel in the bottom of
the carb. If it's cracked it wo't float and just fill up with gas -
that would cause too much gas in the chamber and even with spark there
won't be enough air. Check it to see that it's air-tight. Again,
this is a pretty simple engine and often will start if held WIDE OPEN
and kicked a bunch...

ej2...@yahoo.com

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May 28, 2014, 10:13:24 PM5/28/14
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On Tuesday, May 27, 2014 5:56:55 PM UTC-7, ej2...@yahoo.com wrote:
> okay, now the fuel seems to be mixed but dripping out of the exhaust where the muffler is connected. I maybe getting too much fuel? I checked for spark and its good.is there something im missing?

today the bike started, thanks so much for all the help Gozer!now I just have to fine tune the air/fuel mixture or idle. what type of oil do I use for the transfer case??

ej2...@yahoo.com

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May 28, 2014, 10:32:56 PM5/28/14
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the bike seemed to start when I pushed started it, than kick starting it. I also took apart the oil injector. after I did that it seemed to burn more white smoke as I kicked started. that's when I decided to push start it and it fired up.I ordered a gasket for the transfer case. it should be here tomorrow.
Also the bike was my fathers when he was a kid. When I was growing up I always tried to play with it but now I want to fix it for my kids. I would be awesome for my dad to see my kids riding it. Thanks so much for the advise..

Gozer

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Jun 2, 2014, 3:09:37 PM6/2/14
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Awesome! Glad it got runnin'!!!! These bikes were really simple back
in the day and so were the fluids. I rebuilt mine and used Yamaha's
offering for 2 stroke injection in the oil reservoir (mixing with the
gas) and a synthetic 10-40 - the same thing I use in my modern 2
stroke MXers, BUT here's the kick - back in the day, as well as
recommeneded in the manual, is nothing but 30 weight motor oil! And
that simple oil worked for everything!

Okay, Bud! Hope your kids have fun!!!

ej2...@yahoo.com

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Nov 2, 2014, 1:02:32 AM11/2/14
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Hey gozer, do you happen to know the correct spark plug gap? Or type of plug? I think the aftermarket plug may not be the one it needs

kxdude4

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Nov 5, 2014, 2:50:46 PM11/5/14
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On Sat, 1 Nov 2014 23:02:31 -0700 (PDT), ej2...@yahoo.com wrote:

>Hey gozer, do you happen to know the correct spark plug gap? Or type of plug? I think the aftermarket plug may not be the one it needs

Hey!

I have half the info you want but you can research the rest. I have
the Clymers Manual and it does NOT give the gap (but plugs come gapped
correctly and new oens are cheap for this bike). The manual says the
correct plug is:
NGK B7HS

Lemme add something, tho. Plugs have changed over time (My KX250 runs
an updated plug and the original plug from the factory isn't even made
anymore...), and I would have NEVER used a plug that wasn't
recommended. For 30 YEARS I ran a Champion N-5, and I'm SURE that
would have been the recommended replacement back in the '70s. When I
rebuilt my JT1 I bought a kit off of eBay with a spark plug, points
and condenser and that plug is a NGK B8ES.It works fine.

Good luck and I hope this helps!

Mike S.

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Nov 6, 2014, 12:31:07 PM11/6/14
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"kxdude4" says:

> The manual says the
> correct plug is:
> NGK B7HS

[stuff deleted]

> When I
> rebuilt my JT1 I bought a kit off of eBay with a spark plug, points
> and condenser and that plug is a NGK B8ES.It works fine.

One of those is wrong as they are different reach plugs. The
E (B8ES) is 3/4" long. The H(B7HS) is 1/2" long. If you need
the H and use the E, the piston might hit it. If you need the E
and use the H, the spark will be up in the spark plug hole
instead of in the combustion chamber.

Mike S.

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Nov 6, 2014, 12:36:03 PM11/6/14
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NGK website says B7HS for JT-1



nos...@my.net

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Nov 6, 2014, 3:48:17 PM11/6/14
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On Sat, 1 Nov 2014 23:02:31 -0700 (PDT), ej2...@yahoo.com wrote:

>Hey gozer, do you happen to know the correct spark plug gap? Or type of plug? I think the aftermarket plug may not be the one it needs


I just looked at my JT! - It's a NGK B7HS. Good Luck!!!

ej2...@yahoo.com

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Jan 17, 2015, 6:17:55 PM1/17/15
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Thank you all! 👍

ej2...@yahoo.com

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Jan 17, 2015, 6:18:20 PM1/17/15
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Thank you all! 👍
Message has been deleted

Chris Coogen

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Sep 22, 2021, 1:12:30 PM9/22/21
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Chris Coogen

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Sep 22, 2021, 1:15:47 PM9/22/21
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Any help on How to remove the throttle cable from the carb on a 1971 jt1?

Michael Sturdevant

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Sep 23, 2021, 1:49:43 PM9/23/21
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Remove the top of the carb. The slide and choke stuff will all come straight out with the top. Pull the coil spring back out of the slide until you can see the funny shaped spring down inside the slide. Remove that with needle nose pliers while holding the coil spring back. Now you can push the throttle cable down through the slide a little bit until the end of it clears, then slide that end over a little to the larger side of the cable hole and it will come out.

Chris Coogen

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Nov 13, 2021, 10:46:21 PM11/13/21
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