Feeling stupid right now, Mikuni carb question?

[MikeBear]

Ok, you'll probably laugh at me, and I'm pretty sure I know the answer, but I'm going to ask anyway. You know, when I was a kid, I was a real "Macgyver" on small engines, but never worked on 2 cycle motorcycle engines. I finally got spark back on my new 1974 Suzuki RV90, so it's sparking again, but still won't actually start just yet. I also haven't replaced the old gas either. I want to at least fire it if possible before I get too deep into it.

Here's the question:

On a Mikuni carb (VM17) when you turn the accelerator, isn't the slide inside SUPPOSED to go up and down as you give it gas, or let off gas? Because it doesn't move at all. The cable up at the accelerator feels wonky, and maybe the ball is broken off inside. I have to work tonight, so don't have time to do more to it.

Thanks for the help, and for not laughing too hard! :drinkup:

 

[mmisterbungl]

yes it is supposed to go up when you pull back on the throttle.

 

[Bonanza Bryan]

Have you taken the carb apart yet?

 

[MikeBear]

Have you taken the carb apart yet?

Nope, and I'm not going to right away unless I have to. I do have a carb kit coming for it, but I'm not taking it down before that arrives. I just want to see if I can get it started before doing too much to it too soon. If I just tear it down right away before anything else, and then still can't get it going, that adds more questions to the equation. After all, I've personally never seen this bike started. I bought it real cheap because it wouldn't start, so that was a plus for me. When I removed the cover to clean the points, it looked fairly clean and new in there. I only had to give 3-4 swipes with an ignition file, and it started sparking. It only has just slightly less than 1300 original miles on it, so probably wasn't driven a whole lot.

I did take the throttle handle apart just before leaving for work, and it's messed up a little in there. I think once I get that straightened out, I'll be good to go. Once I have it running, I'm going to change all fluids, adjust everything, and go right through it. Once I know it's good to go, I'll work on the little rust removal and a little paint here and there.

 

[MikeBear]

OK, I found out that the top cap-screw on the carb was unscrewed most of the way. Maybe due to vibration over the years, I don't know. You can't easily see any of this, because Suzuki hides the carb inside of a engine cover, and there's a big rubber cap over it. The unscrewed cap, made the throttle cable loose inside, and the little end came out of the keeper on the bottom of the slide. So, the slide couldn't go up and down when I used the throttle. I got that all sorted out, reconnected, and re-screwed back on. Slide now goes up and down when you move the throttle.

Everything appears to be put back the way it should be, I even hit it with a shot of ether however, I still can't get the bike to start. It doesn't even "pop". I know I have spark, I do have gas getting to the carb, but no joy. I didn't rebuild the carb yet, because my carb rebuild kit hasn't arrived.

Any more ideas?

Maybe the float in the carb is stuck or something, and I just have to do the carb rebuild, and that should do it? I really want to get this going, but I'm not very strong yet/haven't recovered my stamina from back surgery, so I just can't work on it for very long at one time. It's also so humid up here right now, and the mosquitoes are NUTS and eating me alive.

 

[vette66_00]

Its possible the reeds are shot. Bad reeds can cause it to not pull fuel from the carb. Try a little ether in the spark plug hole. If that works then you have bad reeds.

 

[MikeBear]

Its possible the reeds are shot. Bad reeds can cause it to not pull fuel from the carb. Try a little ether in the spark plug hole. If that works then you have bad reeds.

Is bad reeds likely with a bike that only has 1,300 miles on it total? Then again, even with low mileage, it is 37 years old. I'll try the ether in the spark plug hole, that is a good suggestion.

 

[oldsledz]

How old is the gas?

 

[MikeBear]

How old is the gas?

Well, that's a real good question. I don't know. It's the gas that was in it when I bought it. Seller claims it was running last year, but there's no way to tell for sure. Even if it was new then, it's old now.

I had to get spark and get that throttle hooked up and working first, now that they are, I agree it's time to replace the gas and 2 cycle oil with new, and shoot some ether into the plug hole and see what happens. I knew I'd have to do all that anyway. I was just hoping I could get it started at least once before going through the whole thing.

 

[oldsledz]

I would get rid of the old gas to start with, have you done a compression test?

 

[MikeBear]

I would get rid of the old gas to start with, have you done a compression test?

Nope, I just simply haven't had time yet, it's just been real busy lately. I knew it didn't spark, so I got that fixed, and I then found out that the throttle was disconnected, and I fixed that. I only brought this home late Wednesday night. My stamina is still so low, I just can't work on it for very long periods.

Since then I had to get the title searched and cleared (it was, took 2 days due to the States computer system being down), I've had physical therapy Thursday, Friday, and today, and I've had to work Sat and Sunday. So, I'm going at it pretty slow. I do have a compression tester, and I'll check it when I pull the plug tomorrow.

 

[jesse8931]

Mike what ever you do do not bypass the oil injection Suzuki has the main crank bearing covered and only can be oiled with the oil injection system

 

[MikeBear]

Mike what ever you do do not bypass the oil injection Suzuki has the main crank bearing covered and only can be oiled with the oil injection system

Yup, thanks Jessie, I'm wise to the way the oil injection works on this engine. I noticed the oil lines going to several places on the engine.

 

[jesse8931]

Yup, thanks Jessie, I'm wise to the way the oil injection works on this engine. I noticed the oil lines going to several places on the engine.

Ive seen a few of those bikes dead because of premix. And if it were me I would clean the carb very good change the gas and make sure to run the right ngk plug and she should run.

 

[MikeBear]

Since my posting last night, I have now also drained all the old gas (was in the bike when I bought it), and replaced it with fresh gas. I only have one of those "hold on" compression testers, not a screw in type. Makes it a little hard to hold it, and do the kickstart, but I was able to get it over 90lbs before I couldn't hold it down anymore. I'm sure it'll go higher. So compression should be ok.

I have replaced the spark plug for a new NGK BP6HS the manual says should be the right one. I even put a shot of ether in the spark plug hole. However, I still can't get it to start. It tried a tiny bit twice, but that's it so far. Looks like rebuilding the carb is next, maybe ignition timing also. Hopefully that'll finish the job of at least getting it running.

 

[MikeBear]

Wish me luck!

Well, I just spent over 3 hours rebuilding the carb, putting it all back together, and reinstalling it back on the bike. I also changed the tranny oil with synthetic. I don't have the balls to try to start it up at 3:30am in the morning, since it's a 2 stroke! :hammer: <<< my neighbors and wife, if I did

So, I'm going to try starting it about 3pm, after I'm ready to start my regular day. I have to work Monday night, but it's double-time and 1/2 for 12 hours, so I'll get over it. :thumbsup:

I just hope the bike will actually finally start, and then I'll be happy my entire shift... :laugh: If not, I'll be doing this: and this: :crying:

Oh, I'm wondering if I should drain and replace the two stroke oil in the injection tank? It's almost full, but it kinda looks green to me. It's at least 1 year old. Anybody ever seen greenish looking two stroke oil? It's supposed to use Suzuki cci oil, but I always though two stroke oil was more BLUE colored? Maybe the injection type oil is more green?

 

[MikeBear]

Still no joy...

Well, that's it for now. I just spent over an hour on it, and I still can't get it to start. It tried a few times, just a tiny little back-fire, and a slight kick-back on the kick starter. But no complete start. My leg and foot is all kicked-out.

Carb has been cleaned and rebuilt. Air screw is set at 1.25 turns out. Brand new gas, it's definitely flowing to the carb, and I know the bowl is filled (there's a drain screw at the bottom I can loosen to tell) I tried a new plug, then went back to the one the owner had in it, because it seems to spark better. When I had the carb off, I looked into the engine hole, and I can see the reed valve, and it seems ok. The spark plug is sparking, and there's compression.

It HAS TO START, this just doesn't make any sense to me... Since there's compression, I also don't think the engine seals are bad, but maybe I'm wrong.

Anybody have any other ideas?

 

[george3]

Does that engine have rotery valve? if the carb. is inside the caseing on the right side its rotery. is your plug wet when you pull it out?

 

[MikeBear]

Does that engine have rotery valve? if the carb. is inside the caseing on the right side its rotery. is your plug wet when you pull it out?

Carb is inside the right case, but it's a Reed valve engine for sure, not a rotary valve. Yes, plug is a little wet when I pull it.

I have a flywheel puller coming, and it should be here tomorrow. I'm thinking to pull the flywheel, make sure timing is correct, and do the ole "sand clean the magnets and magneto coil transformer ends" routine to it next. Maybe my spark just isn't quite hot enough, or the timing is off a hair. I bought this as a non runner, and I don't know what's normal spark on them. I do notice that the spark seems to kind of circle the plug electrode, instead of being in the middle. Does that means anything? I did have to clean the points to get a spark at all. Just a couple swipes with a point file.

The previous owner claims it was running when he put it away last year, so I don't know. Everything looks good, engine is barely broken in even according to Suzuki specs, it does a little pop, and the kickstarter fights back a bit, so it's trying to start. I've got to be close, and these are real simple engines, so it beats me why it's playing hard to get! :laugh:

Do oil seals in a 2 stroke like this require tearing down the engine to replace?

Heh, one good thing, is by the time I get this thing running, I'll be an expert in all it's settings, and how it's all supposed to work.. Just because it's being a pain, and making me go through everything...

 

[MikeBear]

Good news, and BAD news!

Welp, I know what's wrong with the engine now. The flywheel is spinning without properly turning the crankshaft....

That's the good news, which means once I get them locked together and timed properly, it should start.

Here's the bad news: The flywheel NUT is completely loose, and when I try to remove it, OR tighten it up, it just spins on the shaft.... In fact, I can slightly rock the nut a little. I'm not positive, but I suspect maybe the previous owner tried the "ball peen hammer" trick to pop off the flywheel, and very slightly peened over the end of the crankshaft. And damaged the nut in the process.

IF I'm truly lucky, it's just the nut itself that's stripped, and I can find someway to get it screwed off. IF I'm unlucky, the crankshaft threads are stripped, which means a new crank, and a total rebuild. Which isn't easy on an engine like this. Which means I'd probably be better off to put a 140cc GPX 4 stroke crate engine in it instead of a rebuild. That's a lot less work, even if I have to do some adapting of the frame mounts.

I've grabbed the nut with a locking pliers, and tried pulling OUT while turning, but I can't get it to unscrew. Can anybody think of any tricks to get that nut off? There's not much room between the sides of the nut, and the inner part of the flywheel, but I'm thinking about cutting down a hacksaw blade, and trying to saw through the nut. Also, the inside of the flywheel is threaded, so you can screw in a flywheel puller to remove it. So, I don't want to damage those threads.