HELP, cant get it to start for the life of me

You can get a pack of these 7/32" vacuum caps at the auto parts store. They are the perfect size. You still need to retain them somehow though. A fart or backfire through the carbs can blow them off. Use some sort of small clamp, spring clip, or a wire/cable tie .....



Hopefully you haven't hurt anything. Get spark again and maybe things will be OK. I can't believe it ran very well with those ports open. Usually, the bike pops and spits like crazy. That's how you know to look and see if a cap has gone missing.

ahhhhh that explains it. When I first start this back during the time it was running it would always pop a couple times until it is warm. After it was warm and I turned the choke off it ran like normal or what I though was normal. It idled well and did not pop anymore. Ill play around with it tonight and see if I cannot get spark to appear once I ground the plug this time around.
 
Hey Dann,

Welcome to the forum, nice looking bike!

I bet your head is spinning, huh? My recommendation is to not panic just yet, take it one step at a time, and see if we can't get this bike back and running...then get it tuned, etc.

It does sound like a few things are amiss...but they may not be all that bad. The info you provide will help keep the assumptions from our perspective at bay.

1) When starting the bike, do you use the choke? Once the bike was on, did you turn off the choke?

2) Those vacuum ports were for your petcocks on the tank to allow fuel to flow when the engine runs... if the petcocks are not stock, then those barbs were probably capped when you first got the bike, and likely have come off during riding... you definitely need them capped and that is likely the main reason your bike hasn't been able to start (Assuming all else was fine prior). You can get caps temporarily...or you could get one long hose and connect the two (one on each side) together... either way, that will help with the air/fuel situation to get the engine to run.

3) Your spark tests definitely need to have the plug grounded to have spark since you're relying on kick-start.

4) Not sure on what all was done with your carbs...but leave them alone until the rest of the items get sorted out...

5) Compression test seems WAY low...and could be a result of current situation...but I wouldn't sweat that for now.

If it were me, I would first check the oil and see if it smells like fuel...if so, drain and replace; probably wouldn't hurt to add a little bit of Marvel Mystery Oil in each cylinder (just remove spark plug to get to access); I would test for spark, one plug at a time and grounding each plug...if they have spark move on; I would cap those vac barbs; I would make sure gas was in the tank and flowing to the carbs, and then I would give it a kick or 20...

You could check timing, etc...next but that's where I'd start.

Good luck!
 
Hey Dann,

Welcome to the forum, nice looking bike!

I bet your head is spinning, huh? My recommendation is to not panic just yet, take it one step at a time, and see if we can't get this bike back and running...then get it tuned, etc.

It does sound like a few things are amiss...but they may not be all that bad. The info you provide will help keep the assumptions from our perspective at bay.

1) When starting the bike, do you use the choke? Once the bike was on, did you turn off the choke?

2) Those vacuum ports were for your petcocks on the tank to allow fuel to flow when the engine runs... if the petcocks are not stock, then those barbs were probably capped when you first got the bike, and likely have come off during riding... you definitely need them capped and that is likely the main reason your bike hasn't been able to start (Assuming all else was fine prior). You can get caps temporarily...or you could get one long hose and connect the two (one on each side) together... either way, that will help with the air/fuel situation to get the engine to run.

3) Your spark tests definitely need to have the plug grounded to have spark since you're relying on kick-start.

4) Not sure on what all was done with your carbs...but leave them alone until the rest of the items get sorted out...

5) Compression test seems WAY low...and could be a result of current situation...but I wouldn't sweat that for now.

If it were me, I would first check the oil and see if it smells like fuel...if so, drain and replace; probably wouldn't hurt to add a little bit of Marvel Mystery Oil in each cylinder (just remove spark plug to get to access); I would test for spark, one plug at a time and grounding each plug...if they have spark move on; I would cap those vac barbs; I would make sure gas was in the tank and flowing to the carbs, and then I would give it a kick or 20...

You could check timing, etc...next but that's where I'd start.

Good luck!


thanks. Yeah I will ground and check the spark again tonight. if I get spark I will check the oil makes ure there is no smell of fuel and flush it if I smell some and attempt to kick it after plugging the barbs. If that does not work I'll spend the weekend redoing the timing (I may have to since I replace the points yesterday when troubleshooting and I think that throws off the timing) and go from there. I'll keep updating this thread. I truly appreciate all the help I got so far!!!
 
I can't believe it ran very well with those ports open. Usually, the bike pops and spits like crazy. That's how you know to look and see if a cap has gone missing.

That's what I was thinking...with one of those barbs open, I can usually keep the bike running on the other cylinder, but with both gone...there's no way to keep the bike from stalling unless it's running extremely rich.
 
yes i took his word for it. He seemed like a good guy but it was a mistake on my part for not checking myself. I never did a compression check before but bought a kit just to be on the safe side. When I did check at home both cylinders were at the exact same compression. 62 or so PSI. I'll probably use the compression tester on my honda which starts fine and see if it reads higher than 60 to rule out any issues with the test itself. As for performing the test I simply took off the carbs completely, took one plug out and plugged the tool in a kicked 5-6 times and it would not go past the 60 mark.

If I missed something please let me know. I dont know of any mechanics in my area familiar with compression testing so I'd have to tow it to a shop to get it done correctly.

When you buy used cars/trucks/bikes, there is no such thing as a "good guy". They have something they want to sell, and believe it or not, they sometimes tell lies. If they suspect you are not experienced with bikes, they will tell you what you want to hear. I hope you didn't pay much for the bike, because you are going to be paying out quite a lot of money very soon.

Seems like he forgot to tell you about the missing master cylinder reservoir. I wonder what else he forgot to tell you.
 
That's what I was thinking...with one of those barbs open, I can usually keep the bike running on the other cylinder, but with both gone...there's no way to keep the bike from stalling unless it's running extremely rich.


If i assume this is true then how do I adjust the mixture when I cap it? Is it as simple as turning a wrench or screwdriver?
 
Yep...you should have BS38's carbs (stock for '78)...which have an adjustment screw (right behind the choke lever on the left and right sides. These can be turned in/leaner or out/richer for the idle. Stock setting is 2 1/4 turns (I think) out from fully closed. I wouldn't mess with them just yet, just see if you can get the bike to start with the caps on first.
 
If i assume this is true then how do I adjust the mixture when I cap it? Is it as simple as turning a wrench or screwdriver?

You have a lot to learn about these bikes. Instead of asking 20 questions, you need to go to the "Tech" section and read the "Carb Guide". You have to spend time educating yourself, at which time you will be able to ask proper questions.

Members on the site made the effort to write up how to work on and tune the carbs. Now its your turn to read it.
 
I should have added...to fine tune each carb, you should learn to do the dead cylinder method... there are some threads on here about it, but you essentially need to get the bike running (so usually the stock setting is close enough) and balance the carbs... and then try to get the idle down to the lowest it can go before stalling out... then you kill one cylinder (I usually pull the spark plug wire, put a machine screw in there, then with a jumper wire, I jump it to the top of the spark plug that's still in the cylinder...start the bike, and touch a screw driver to the spark plug....that shorts the plug and cylinder stops firing).

The goal here is to get the other cylinder that's not shorted out to run at it's fastest/smoothest rate by adjusting that mixture screw a 1/4 right or left or whatever works best...with a slower idling engine, it's really easy to hear the best spot... then repeat for the other cylinder.

Again, this is not a detailed process here...but a general summary.
 
About that rear brake, running a little tube like that is common in the chopper community. Though it is usually done on the front to keep the bars cleaner, not saying it's good or bad, just clarifying. It wouldn't change the look much to run a legit MC back there so maybe consider that once you get some of these other issues sorted out.
 
The mix screw is for fine tuning and adjustments. I don't think it will be enough to compensate for open (then closed) vacuum ports. I guess it's possible the P.O. "tuned" the carbs to run with those open ports. I think that would take some pretty big jets though, especially for the low speed or pilot circuit. Bigger than you would normally use for the mods you have (pipes and pods). You're going to need to check what jet sizes are in those carbs eventually. You need to know this anyway for tuning purposes. Here's a chart I made up showing the stock sizes. The usual routine for your '78 carb set and with your mods would be 1 or 2 up on the pilots and 2 or 3 up on the mains. Mikuni jets are sized in 2.5 increments .....

 
If the PO "tuned" the carbs with those barbs open, what does that say about the PO's knowledge of carbs in general. I would be very suspect of mechanical and electrical items on this bike..................could be more hidden traps waiting.
 
If the PO "tuned" the carbs with those barbs open, what does that say about the PO's knowledge of carbs in general. I would be very suspect of mechanical and electrical items on this bike..................could be more hidden traps waiting.

Or a more optimistic view could be that everything was tuned and running well until the caps came off, and that's all there is to it. lol.
 
I think he said they were open when he bought the bike. But that could mean they were open by the time he drove it home, lol.
 
You have a lot to learn about these bikes. Instead of asking 20 questions, you need to go to the "Tech" section and read the "Carb Guide". You have to spend time educating yourself, at which time you will be able to ask proper questions.

Members on the site made the effort to write up how to work on and tune the carbs. Now its your turn to read it.

I took your advice and read through a couple of the carb basics on the tech thread. Im going to be honest, a good portion of it went over my head but from what I can tell there are a couple different adjustments I will need to make to fine tune the carbs.

Please let me know if I'm on the right track but when I took the carbs apart to clean I noticed that fuel was coming out of the driver side carb in the holes right where the pod filter connects to the carb. I did some research on that last night and found it was probably due to the float not closing all the way. Unfortunately I did not catch the fact that there are tolerances for the float and measurements I needed to adhere by so I just went in a bent the float flap (portion of the float that presses on the mechanism that closes the valve) in just a little and put it back together and noticed the carb was not leaking anymore. Since the passenger carb did not have this issue I did not tamper with it.

Looks like I need to figure out what carbs I have and if they have been modified with larger jets. How do I find that???? I could not find a model number or anything on my carbs when I pulled them last night so I dont know what kind I have so I've been assuming they are stock.

Looks like when and if I get it started I should sync the carbs using the oil in a tube method and the barbs I am expected to close off.

Is syncing the carbs the same as tuning? If the oil in my clear tubes are aligned with each other does that mean it is tuned? I could not find the difference in the documents or maybe I missed it.

As for my starting procedure I know a couple of you asked if I rode with the choke on. I only applied the choke to keep the bike form dying when I first cranked it on. At first I just adjusted the idle screw to increase the idle but noticed after the bike warmed up I had to drop that screw otherwise my idle got way to high. Instead of doing that every time I started the bike I just tried to run it with the choke on for a few minutes until the bike was warm before I turned the choke off and left the idle screw alone (still idled too high for my liking when I rode it the first time)
 
Great! Glad you found the tech section and carb guide...they are great, but until you start playing with the carbs, it can feel like gibberish. Then you'll have this, "aha" moment...and it will all make sense...or moreso at least. :)

Float heights are important...so that's a must do. There's a lot of threads on how and where to measure them.

Carb syncing is different than tuning. Essentially you sync them so they are equally balanced for each piston and when you pull the throttle, both carbs give the same fuel ratio and keeps the engine from vibrating, etc. Whereas you tune each carb to run the most efficient/smoothest to provide the best mixture of gas/air to each piston, providing the best compression possible, and in turn have a strong performing, well balanced and long lasting engine (running similar temps, etc).

The easiest way is to measure the vacuum in each cylinder (Yes, using those barbs on the intake manifolds)...a simple hose (that fits those barbs) with oil and as the bike idles, one carb or other will have more or less vacuum...you simply turn the center sync screw to adjust the right carb to the left's volume.

However, you can only do this when the bike is running...until then, a bench sync is needed. There's threads on this as well...but essentially getting both butterfly valves to be the same works for me. I like to adjust them so that they both have the same slight tension on a piece of thin paper being passed through the bottom. It's kind of a feel thing. Ultimately, you're looking for the same distance/gap.

Note: Adjusting the idle as the bike warms up is normal for these bikes... but I do the same, I let the choke stay on for a minute or two and then it is warm and runs great without it. I don't ride the bike with the choke on though...don't think it would hurt anything, but I was told not to when I first started riding back when I was a kid and so I don't.
 
THANK ALL YOU FOLK AND JESUS lol. Its started!!!!!! So I tried grounding the spark plug and kicked it a few times still no spark. I then grabbed my jump box and placed the positive on the capacitor positive and the negative on the frame. I turned on the jump box, grounded the spark plug and kicked and saw spark!!!! I was very excited. I then went to install the plug, block off the nipples on the intake manifold that was open and kicked it a total of three times with no choke and for the first time it started in three kicks with NO CHOKE!!! I've never started it with no choke. It ran much smoother (no popping) once I blocked those barbs off. I didn't let it run long since I had wires everywhere and fuel leaking from the petcock (just started leaking since I messed with it last night)

I'm going to spray it off an install a battery. Could the capacitor be bad since it starts with a battery???

Once I let it warm up I'll redo the compression test.
 
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