Blaster Help me diagnose this problem? (Won't Start)

[retroicon]

Hey Everyone,

Thanks in advance for any help you can provide... I'm lost at this point.

I had a motor rebuilt a while ago (a few years) and just finally found the time to put it back into my Blaster. It's a 62t, dual 44's, MSD Enhancer, Lightened Flywheel (Zero), 4mil stroker (plate), Girdled head (185 compression), Factory Blaster pipe, coil from JSS.

The motor was rebuilt with new rings, fresh hone, carbs rebuilt, new Enhancer, all new fuel lines.

Leakdown test is good, compression is good, I can see fuel running through the lines to the carb (see it through inline fuel filters), I have strong spark on both cylinders. I can also hear fuel going through the return line, and dropping into the tank which seems to indicate that the carbs are pumping plenty of fuel.

The primer is on the return line, and when I open the gas cap after trying to start it for 20-30 seconds, I'm getting that "vacuum" sound that indicates the tank is pressurized.

If I put a couple of drops in each cylinder, and replace the plugs, it'll fire for about a half a second, and that's it. (yes, a few actual drops)

So with fuel it'll at least fire.

Where should I be looking? I have an idea what I have to do, but I'm just asking for a few opinions before I start pulling things apart.

Based on what I've said... compression good, leakdown good, spark good, fuel going through carbs, and into return line, tank pressurized, will briefly fire if fuel is dropped into cylinder. Where would you start first?

Thanks
-G

 

[retroicon]

Nothing huh?

 

[Pro-pulsion]

Timing marks are an easy to look at start. I have also read on numerous occasions that the MSD enhancers can be defective right out of the box or will only last a few rides and then fail. If the timing marks are good, unplug the start/stop switch and test it for continuity. I don't know if the service manual has a resistance value for them but if they are anything like a typical "normally open" or "normally closed" switch and having nothing more than just connection between the circuit, then it should not read higher than 0.3 ohms of resistance. Anything above that and you have a failing switch. You could also check the little fuse in the e-box to make sure it is still looking proper. If your ski had the thermal sensor for the stock head, is it still attached or did you remove it? If you have to start really digging, one other easy to check but dig a little spot is the carbs. Check the black metering diaphragms to make sure they were not installed upside down. If the little center posts are not contacting the needle valve lift arm then no fuel will go through the carb throats, just pumped back into the tank...good for saving fuel though

 

[blaster800]

sounds like its not getting FUEL . engine has been sitting a FEW YEARS ? better go through the carbs !...... check needle and seat for being stuck or SOMETHING else in carb IMO . thats where I would start . good luck

 

[Pro-pulsion]

I had a motor rebuilt a while ago (a few years) and just finally found the time to put it back into my Blaster....

The motor was rebuilt with new rings, fresh hone, carbs rebuilt, new Enhancer, all new fuel line

I believe the engine and new carb kits have not yet seen fuel prior to installing it in the hull. This is how I am interpreting his description.

 

[augustaf]

Well for the primer to work if installed in the return line as stated by op, it would have to have a loop down to the bottom of the hull that contains fuel from previous running. That is one issue. The carbs are apparently not getting gas either, the carb fuel pump(s) should fill the filter almost immediately after engine start (after having dripped gas into the engine as stated above)

 

[Quinc]

Make sure the fuel "IN" line is on the bottom nipple and the return line is on the top.
If you are running a fuel on/off/res switch, get rid of it and run the lines directly to the carbs.
Check your spark for a good 10seconds or so. With my msd it would spark for about 5-6 seconds before it would stop
open your low speed screw and idle screw
is your jetting correct? To lean to start / to rich to start?

 

[Rushford_Ripper]

I had a start/stop switch that would cut the motor out, only ran a few seconds and dead. Maybe clean the contacts inside of the switch?

 

[BruceSki]

Needles are stuck closed and not allowing fuel in.

I think frank hit the nail on the head.

I had it happen with a carb I took apart 2 months ago. Went to fire it last week and no fuel. Popped needle open and lubed it with some wd-40 and bam. Fired right up.

 

[retroicon]

So as is always the case, I'm back.

Don't you hate it when you give a bunch of advice, and never find out of any of it actually worked?

So just to clarify, the motor, and carbs were both previously used, then re-built, and then sat a few years after the re-build. No fuel had been through the motor, or carbs, until I tried to fire it up.

This was like a brand new install. New fuel lines, dry tank, nothing every through the motor or fuel lines until a minute or so before pressing the start button.

The fuel lines were in the proper spots, direct from the tank, with no on/off/reserve switch in line. The carbs were both set at 1.5 turns out on both the high, and low speed adjusters.

I'm not sure what the issue was, but I suspected carbs like everyone else seems to be thinking. With strong spark, fresh rebuild, new parts, no air leaks, etc. (start stop swtich was brand new, probably should have mentioned that)

I have NO idea how I got fuel into the return line as the motor had never been run, and that means there couldn't have been any residual fuel in there.

That, to me, meant that fuel had to be running through the carbs (or at least one of them) and going directly out to the return. (not sure if/how this is possible?). I'd tried cranking it for a good 2 minutes in total (10 seconds on, then another 10 seconds, etc). Anwyay, I figured before pulling the carbs and opening them up, I'd give it 3 more attempts.

Charged up the battery as it was running down from all the previous attempts, and gave it the last shot.

Attempt 1. 1cc of fuel in each cylinder. Fire, then nothing.

Attempt 2. 1.5cc of fuel in each cylinder. Bigger fire, then nothing.

Attempt 3. 2cc of fuel in each cylinder. SUCCESS!

I'm not sure if something was stuck in one or both of the carbs that rattled loose, or finally vacuumed loose, but it finally fired. I thought it was a fuel delivery issue, and it turns out it was.

Thanks to everyone who chimed in.

I guess the lesson here is... if you think everything is right, give it one more shot before you get out the tools. I checked that spark was, knew the leakdown was good, plugs were brand new, fuel was fresh from the pump, carbs were freshly rebuilt, and I really thought it should fire.

Before tearing everything down, give it one or two more chances. Who knows, maybe you'll get lucky like I did.

-G

 

[SXIPro]

The real lesson is even freshly rebuilt/cleaned carbs can have things 'stick' or get hung up, especially afer prolonged sitting. It happens all the time.

 

[BruceSki]

I bet the needles were stuck and you dumping fuel down the cylinders and running it pulled enough vacuum or vibration to pop them open and function correctly.

Next time on a fresh rebuild, double check that you have fuel flow from the return. Manually choking the carbs with your hands helps pull fuel on a new setup as well.

 

[yamanube]

Was just working my way to the bottom of the page to say exactly what Bruceski said. I always choke the carbs with my hands to get them to pull fuel for the first time, it gets the fuel lines primed quick without running the motor lean.