Trail Boss/Blazer carbs didn't change that much over the years. Mainly the jets if anything.This old VM30 Mikuni was used from almost day one until production ended.Plus here's a couple videos on this style of carb.

 

Awesome videos. I think I will be doing this type of cleaning for sure. I just ordered the carb kit, but from MFG Supply as they were cheaper. I had previously ordered oil seals from there. Quick shipping

Thanks

 

Well I received carb kit and today I had time to pull carb and rebuild it.


The results were no different than before. I killed the battery trying to start it with the starter and wore out my right arm using the pull start. I then noticed my tank was almost empty( it was half full before I started).


I could also see fuel dripping from exhaust. I pulled crank case drain plug and found the majority of my missing fuel.


I cannot figure out what is going on with this thing.


To date I have had top end bored .20, new piston, rings, gaskets, oil seals, carb kit, starter rebuilt, new fuel lines and filter, a few new spark plugs, new air filter.


I have fuel, spark, and I hope enough compression.


I am trying to figure out why all my fuel keeps dumping into my exhaust and crank case. I have a new float needle and the floats are set to spec.


I can't see almost 1/2 tank of gas getting through just from a few minutes of cranking it over.

After draining out all the fuel, I did manage to get it running. It still doesn't have any pep to it. I can give it a shot on the throttle and it is very slow to respond and feels like it is being choked off. I can pump the throttle slowly until the revs pick up and only when the revs are higher does it respond faster to the throttle.

Stumped

 

Don't hope on compression,check it even if you have a new top end.That plus sounds like the float needle is sticking if the engine is being flooded. Get all the gas out,pull the engine over several times to clear the cylinder and do a compression reading with throttle wide open.

 

Very frustrated.. .lol


I am popping the top end off to check everything out. I just don't think I am getting an accurate reading from my compression tester.


Pulling rope to turn over engine, I have absolutely no resistance like I do with my other 2 strokes. No kick back, nothing. What I mean by no resistance, would be like laying a rope on the ground and pulling on it. That's how little resistance I have.


I am also going to check seals to make sure they haven't failed as well. Troubleshooting this has been exhausting and now I am just going to start fresh with a tear down.


I believe now, the top end work I had done was a crappy job due to the exact same issue I am having before I even had the work done.


Time will tell once I have this tore down.

 

Tore it down this morning.


Everything looked good as far as I could see. I checked ring gap clearance, but it seemed way out according to manual. I could easily slide in a .60mm gauge in the gap. Manual shows .008-.016. (not sure if that is metric as manual doesn't state this)


I am thinking that is a bit large. Cylinder walls looked good with no scratches or gouges and could still signs of the bore. There are a couple scuff marks on cylinder walls, but they don't appear to be scratches as they are smooth and I cannot catch an edge on them.


Here are pics ...








the next pics might not be accurate ....

















I am wondering if I should take it in and have it professionally checked as I am thinking this is where my issue is???


Thanks

 

Yes take it in as digital calipers aren't as accurate as a set of micrometers. Ring gap is way too wide just looking at it,plus who bored this cylinder?? Again max clearance you want to have at the piston skirt and the cylinder base is between .0011-.0021 per the manual. Service limit before rebuild shows .006,but that's stretching it a bit imo. Plus looks like the cylinder wasn't cleaned up all the way when it was bored looking at the darker area and scuff marks around the ports or was bored too much. Plus first pic is correct on point to measure at the cylinder base. Pic #2 is not correct. Needs to be measured at the bottom of the piston skirts.

 

Finally got my top end back from dealer. What they found was previous bore was out of round and needed to be redone. My mistake for originally taking to someplace else trying to save a buck.

So it is again rebored and new top end kit. It was a bastard trying to put in those circlips.

Just finished putting back together. Compression check on cold engine is reading approx. 124.

It's going to be a few days before I can fire it up. Need to fix petcock as I cannot turn it by hand.

 

Kinda what I thought when I saw the dark spots in the cylinder and around the port where the boring bar missed.

 

Filled up tank with 40:1 and running oil pump. Fired up first try and drove around yard for a few minutes. Still lots of compression.

Going for a trail ride in a few days. Finally have both tri motos rebuilt and trail boss running.