2000 Blaster will only idle

[aerospot]

This has me stumped and I am hoping someone here can help.
My grandsons 2000 blaster has suddenly quit running and I am working through process of eliminating what the potential culprit could be.
It will fire and run only at an idle. Opening the throttle only results in flooding it out. No change in rpm when working the throttle, only more gas getting sucked in.

1. checked fire good
2. checked carb took apart and cleaned w/ no sign of issue.
Replaced and tested, gas flows up needle as req.
Reeds were also checked with no issue.
3. checked muffler Suspected muffler may be clogged, removed with no change.

I did a compression test and only got 75 – 80 lbs. Pulling the head, I noticed the mating surfaces wet and a wet spot on the fins of the head and cylinder indicating blow-by.
Using the old gasket I cleaned everything up and re-torqued the head down. Same scenario, no rpm changes, only idle.

A friend suggested that with the lack of compression and obvious need for a top-end is the cause. But I cant figure out why it would still idle if this were the case. I plan to do a top end anyway, but would like to pin down this issue if indeed it is not related.

I’ve replaced the mag coil, ignition coil, cdi box. If not the top end, I’m at a loss…

 

[joeak47]

Not to sound stupid,but have you had the air filter off for any reason and perhaps left a rag in the boot or something?

 

[joeak47]

Also... how old is the fuel?

 

[motoman159]

Um, rebuild, you should have ATLEAST 120 lbs of compression

 

[joeak47]

Also check to see that the parking brake isn't set while trying to rev it up. This will cause the TORS to to tell the cdi not to advance, not letting it get past idle (safety feature). When checking compression,don't forget to add 3.4% for every 1000ft in altitude. Manuals show compression readings at sea level.

 

[best]

I bought a freshly rebuilt 1974 DT250 many years ago that did the exact same thing.
Turned out the piston was in backwards. Pull the exhaust pipe off and see if you can see windows cut in the piston skirt?
The windows should be on the intake side.

Worked pretty good once that was fixed up...

 

[bummer981]

Sounds like an issue with the TORS system, remove it.
http://www.blasterforum.com/do-yourself-20/how-remove-your-tors-655/?highlight=tors+removal

 

[aerospot]

Air Cleaner is completely off.
With the head removed, I can see the piston and arrow pointing forward.
Gas is fresh.

I had'nt considered the parking brake but dont see any cdi connection to it. I havent used it either so it isnt engaged but if there is a cdi connection, it may be the issue.
I've checked both ends of the throttle position switches and both are opening & closing as they should.

I measured the jug diameter with the head off and it appears to have been bored at least once. I think I'll have it re-bored and purchase a matching piston / rings to rebuild with. Sure hope this fixes the issue. Grandson is gettin anxious to ride!

 

[aerospot]

Sounds like an issue with the TORS system, remove it.
http://www.blasterforum.com/do-yourself-20/how-remove-your-tors-655/?highlight=tors+removal

I've played with disconnecting the plugs at the carb, throttle lever and both together. Same result each time. I've even disconnected the 'brain' module plug entirely, same same... I'm perplexed.:-/

 

[blasterdemon7]

Did you hold the throttle wide open and kicked it 8-9 times to do the compression test ?

 

[aerospot]

Did you hold the throttle wide open and kicked it 8-9 times to do the compression test ?

Nope... throttle closed
I'll do another today and compare...

 

[aerospot]

Nope... throttle closed
I'll do another today and compare...

Throttle wide open, 9 - 10 kicks I got 90 lbs on the nose. Not great but it should run...

I've also removed all remnants of the TORS including throughout the harness. Gone!

I've even replaced the main ignition coil in the mag.

It starts and idles, but no response in rpm throughout the throttle range. The slide can be seen through the back of the carb. Holding my hand over the opening and chokeing, wets my hand with gas.
There is no noticable blow-by showing through the case vent pipe.

I really thought the TORS was my issue but not..

Would the voltage regulator have anything to do with it??
Would it be something with the carb that I havent looked at?? :-/

 

[best]

All right, try pulling the bottom off the carb and checking the needle and main jet.
If the main jet was loose and fell out it would go too rich very quickly.
Needle is even more likely, if it is broken off or too high or too small.

Yes, should run at 90.

Good luck!

 

[scotj77]

This sounds exactly like your compression is just too low. can you rev the motor without it in gear? it should only die under load from lack of compression. but 90psi is way too low.

 

[JBRoc01blaster]

Sounds like a problem with your reeds to me, take off your carb and remove your reed cage and check for cracked, bent, or broken reed petals. A few months back I had a similiar problem, my blaster would idle but when i put it in gear and let out the clutch it would die immediately. Turned out one of my reed petals fell out, I put in new reeds and she started right up and ran fine. Definately check your reeds if for some reason you havnt already !

 

[aerospot]

All right, try pulling the bottom off the carb and checking the needle and main jet.
If the main jet was loose and fell out it would go too rich very quickly.
Needle is even more likely, if it is broken off or too high or too small.

Yes, should run at 90.

Good luck!

Thanks guys!

I'm heading back to the shop today and try your suggestions.

Best- I'm checking the bowl idea first. I had recently set the needle one slot lower as my grandson rides rather slow and doesnt open it up much. Keeps it from loading up and fouling. I'm skeptical as I have tried covering the back of the carb when running and gas soaks my palm. + I've been through the carb... twice.

Scott - The idle is in neutral, There's no sense in attempting to ride when no RPM change is recognized. It's up on a stand stripped down to bare essentials attempting to reconcile this ongoing issue.

JBR - I have had to replace the reeds last summer when the Blaster 'Ate' one. Having the same suspitions I removed them and inspected while they were still attached to the cage. I'm going to again take them off and remove them from the cage to do a more thoro exam...

This wheeler has not had great compression since we got it early last summer. This hasnt been a problem as my 12 year old grandson is just learning to ride. Still it has always been OK starting and ran fine until the current situation occurred early this spring...

I'm reading about a "Parking Switch" but do not see anything that may resemble it on my 2000 Blaster or the manual's schematic.
I have become quite 'Intimate' with the electrical system on this machine tho...

Thanks again guys! I'll take some pics today and put em up.
My wife has reminded me of a quote I've used before. "Not a small engine I cant master"... 8-|

 

[scotj77]

the parking switch only comes into play after 2003. I was asking if the engine will rev in neutral. if it does it's not a carb problem. if it just shuts down when you try to go it is the compression. but you def need to address the compression problem before you try to diagnose anything else

 

[blasterdemon7]

the parking switch only comes into play after 2003. I was asking if the engine will rev in neutral. if it does it's not a carb problem. if it just shuts down when you try to go it is the compression. but you def need to address the compression problem before you try to diagnose anything else

X2. Running with low compression from a worn bore could snap off a piston skirt and break a hole in the cases.

 

[aerospot]

Reeds and carb are all OK.
Pulled Mag and coil plate as a last place of interest.
I'm probably wrong but dont believe this issue is related to compression, or lack thereof.
Still gett'in the jug done but would like to have this issue solved first..
But if the CDI and charging coils all check out, I'll be out of tricks! Then I guess I'll go ahead and do the top end and see what happens...
It's been an education if nothing else...

 

[Blaaster]

I see no mention of a leak down test being done, do one before you pull the motor apart to try to diagnose why you have lost compression.

It is normal for a little fuel to be spit out of the back of the carb, that is the reason why a paper air filter should not be fitted directly to the carb throat.

When you pull the pipe off to do the leak test, get a look at the piston/rings up the exhaust port.