rm50 no power when shifted to drive??

[jag]

Got a Suzuki rm50 that revs and idles ok. But once shifted into drive there is no power. The bike barely moves under its own power. What the heck is going on here?

There is two screws on side of Carb. I know one is an air mixture screw but what is the other one? Throttle screw? They are side by side..

Please help.

Thanks.

 

[dadof2]

when you say no power can you describe it a little better
as in backfires wont rev has a big stumble but then overcomes it more info is needed

 

[pbk]

is it blowing heaps of smoke??

its either going to be your clutch or it needs a rebuild

more than likely because its such an old bike you will probably need to replace both

 

[jag]

No heaps of smoke.

It starts on first kick. Revs good. but not very quick. Can't just blip the throttle. It's slow to rev high but it returns back to idle pretty smoothly.

Once you shift down, ( only one gear ) it doesn't shift down very smoothly. It knocks into gear like its still idling to high.

Anyways, once it goes into gear and you try and rev it up it will barely move under its own weight. Once it starts moving its pretty slow. I can only check so much cause I can't get on and ride it.


Hope that helps.

TY for the quick responses.

 

[sean01]

find your self the workshop manual for the bike and do a compression test.

the way im reading all this it seems its down on compression but also could be a carb tune problem or even a bodge set of reeds( sht cant even remember if they had reeds)..

the manual will help identify standard jetting and tolerances for the reeds as well..

 

[jag]

Compression seems to be good. It's hard to kick start it.

I've been looking EVERYWHERE for a manual but can't find one.. anyone got a link to a pdf file or anything ?
When you say reeds do you mean "points"? If so I can't find those anywhere.

Spark is good.
It's getting plenty of gas going through the carbs. I've triple checked the jets, no blockages. It doesn't act like there is vacuum leak.

It revs to high rpms in neutral, but NO high revs/rpms in the "drive" position.

It's boggling my mind!

 

[sean01]

well if comp seems good then maybe start looking somewhere else...

reeds fit in the barrel, most of the time there between the barrel and the rubber carb manifold but some were also screwed to the bottom side of the barrel (crankside)

older bikes were known for cracking the rubber manifold and causing an air leak (vacuum leak)
also make sure you not choking it too much with a abnormal aircleaner, and make sure it isnt over oiled..

make sure you have the correct spark plug installed too, and def dont use anything but the proper plug.. at a guess it probly runs a B9ES or B9EV spark plug. B8ES were sometimes used too..

ill try and have a dig around for a manual

 

[jag]

Well I've definitely never messed with any reeds. When you say barrel, do you mean like the intake? Where is it located on the engine?

Vacuum leaks usually create an inconsistent idle, I've never known for a leak to actually cause power loss to this degree.

The spark plug that was in it was an ngk BP4HS.

 

[jag]

Oh and the choke on the Carb is different from what I'm used to. Thks choke has a brass plunger like thing that moves up and down inside the carbuerator. It is fitted on the top right next to the slide and needle.

The bike will rev fine ( in idle ) when the plunger is inside and seated inside the Carb, which means to me that the choke is on. When I push the clutch down, which raises the plunger up, out of the Carb the bike will either rev up real high or bog down immediately and die.

 

[sean01]

choke up for on, and down for off..

ok factory plug was a BP6HS.. should be fine tho.. also check the gap in the plug..

you need to work out what your calling things too cause its causing confusion.

the barrel is the section that the piston runs in.. the head is bolted on top of it.. head obviously is the section with the spark plug in it.

vacuum leaks can have a funny way of showing and not always will it idle inconsistent..
they can cause real snappy throttle response, slow idle return, flat spots etc..

you havent commented on the air filter? if ya can remove it and try the bike.

one other thing.. what 2 stroke mix ratio are you using? and how much blue smoke is it blowing

 

[jag]

Ok well with choke lever up, (plunger down) would be choke on then that means the bike only runs on choke and dies when I let out the choke.....

I have tried with air filter element in and out. No real difference. All it is is a funnel shaped piece of plastic that has a sponge like material in it.

With no manual I don't know what the gap should be but its set at around 26-27.

It does have flat spots, inconsistent idle and is slow to rev up. but thesegaskets look great if not brand new.

it has a self oiled/ oil "injector. no mix necessary. only smoke on cold start.

 

[pbk]

Ok well with choke lever up, (plunger down) would be choke on then that means the bike only runs on choke and dies when I let out the choke.....
.

that sounds like a tunning problem

 

[sean01]

post a pic of your carby, all the ones i seen so far are like a mikuni carb.. they run on the side and pull out for on and push in for off suzuki carburetor rm50c partsmanual fiche rm50 1981 x

actually post a pic of your whole engine, maybe some of the advice iv given on certain things are a little off due to me trying to picture the engine in my head as its been over 20yrs since i seen one of these..

but im pretty sure i know the carb yr talking about and it will work the opposite to wat i said earlier

your spark gap seems fine

is there any identifying numbers on the carby like a serial number or something.. just doesnt seem like a standard carb

 

[jag]

Ok well with choke lever up, (plunger down) would be choke on then that means the bike only runs on choke and dies when I let out the choke.....

I have tried with air filter element in and out. No real difference. All it is is a funnel shaped piece of plastic that has a sponge like material in it.

With no manual I don't know what the gap should be but its set at around 26-27.

It does have flat spots, inconsistent idle and is slow to rev up. but thesegaskets look great if not brand new.

it has a self oiled/ oil "injector. no mix necessary. only smoke on cold start.

 

[jag]

Thanks again for all the input.

It's a mikuni Carb. The only thing I see stamped on the side is ISO..

The fiche you linked isn't the same. This one has only one float and the needle is positioned in a way where I don't think you can get it out.

So I wondered if it can only run on choke if its not getting enough gas but I don't see a tab on the float to be able to adjust the level of gas. This is just speculation though as I've never had this problem before with any bike I worked on.

Carb | Flickr - Photo Sharing!

Dirt bike | Flickr - Photo Sharing!

 

[sean01]

ok if thats your bike in the photos its not an RM50.. its a JR50.
RM50's are vertical configuration engines (barrel and heads points up) and JR50 are horizontal engines (barrel and head face forward on slight upwards angle)

BikePics - Suzuki RM 50 Home Page on BikePics.Com (not your bike)

BikePics - 1986 Suzuki JR 50 Home Page on BikePics.Com (this is your bike)

so more than likely the problem your having is just how the bike performs..
lol you had me thinking when you said it was oil injected..

 

[dadof2]

hmm you may not believe this but i put it down to the coil
had one this week would rev and idle but coff splutter and stall when ridden
it was the coil
showed spark hell it idled so of course it had spark but it broke down under load

 

[jag]

I'm sorry. Haha. Just trying to fix it for a friend. I'll take an ohm reading of the coil and see what it is producing. If that's possible without a battery...

I just don't even know where to begin on this bike tho.

Sorry for the confusion.

The Carb is rebuilt

The gaskets look great. I don't know what else to check.

 

[Cactus Jack]

Plunger down or in is choke OFF ... plunger up or out is choke ON ... Regardless of how a lever is configured ...

2 strokes can also start easy and rev in neutral but die in the ass under load if the crankcase seals are shot or there's play in the crank main bearings ...

 

[jag]

Plunger down or in is choke OFF ... plunger up or out is choke ON ... Regardless of how a lever is configured ...

2 strokes can also start easy and rev in neutral but die in the ass under load if the crankcase seals are shot or there's play in the crank main bearings ...

Okay then its running the way it should concerning the choke. Great..

I really hope it is not as drastic as you say it might be.

I wish I could send a video of it running or describe it better. It's got to be somethin menial and easy. I'm just over looking it.