Went through 3 motors within a month (pics)

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dougstar said:
but your other pic is of the exhaust port .....and its so clean no oil? :unsure:
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I recently swapped to a tuned pipe. Before that my stock canister exhaust would spew hot black goo everywhere, so there was plenty of oil coming out of the exhaust port. Maybe it looks clean because of how hot the engine was running.
 
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dougstar said:
but your other pic is of the exhaust port .....and its so clean no oil? :unsure:
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Too clean ,I always like to see a little carbon build up on mine ,I just clean it out every now & then so it doesn't flake
off an scar the cylinder!

His looks like more of a friction an heat issue from lack of oil lube ,also the high octane ,as I use a cheap 2 stroke oil
an 87 oct ,ive never burned an engine up in 30 years of running any 2 stroke engine of any kind!
 
I should have mentioned that I also have an HPI Baja which I bought used. The motor looks old and I have no clue what it is. It pulls hard so it must be at least a 26cc CY with a 668 carb. I've run about 8 tanks through it now without any issues using the same gas/oil mix that I've been using on the DBXL. I don't think my gas/oil mix is the issue. I measure all my mixes uses that ALM mixing bottle and I make sure I'm precise with it. I notice my Baja smokes at WOT in the top end while my DBXL doesn't. It could just be blow by from the old baja motor, but still seemed suspicious to me. Maybe the 997 carb isn't working properly on the H needle. It fires up every time with less than 3 pulls. It smokes off the line like it's supposed to, just not at the top end.

BTW, is there any issue with running these things for more than 30 min straight? Our group normally does tarmac auto-x style races where we literally run 30 min non stop around the course. I never check engine temps as I assumed they were made to take it. We have a long straight where there's a WOT pull for maybe 5 seconds.
 
It's too lean fuel or your oil mix is off or your oil is crap. You should have had to fatten the high needle up for a tuned pipe vs the stock muffler. The high test pump gas doenst have anything to do with it. Any two stroke engine manual either specs mid grade or high test. Smoke out the exhaust at WOT should have a bit of a haze imo.
 
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Bryan K. said:
I use this ALM mixing bottle. Seems pretty accurate. I'm in Canada, so we use the metric system ;)

5d78d502b5fd73ac0a15cd8b970961428bb260f0.jpg
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I wouldn't use those. They swell very quickly and become quite inaccurate. Great for storing mixed fuel but you'll find that they rapidly start holding more than the advertised amount.
 
Those pictures of the piston through the ports , You ran way to lean . It ate the piston ring that's why you cant pull it over ( the gouges in the piston carb side). Also you can see the piston is actually blue from the heat on the exhaust side.

What ratio were you running for the oil to gas? I think I might have missed it skimming the thread.
 
Those cups are like $9.00 no swelling, no staining. I do have a maxima cup that has a lid, don't know where I got it from. But it has a big lip on the top that holds a bit of oil in. It's not much but I'm sure when your talking ml or oz for a small amount of gas it throws the mix off a little.
 
Bryan K. said:
Maybe the 997 carb isn't working properly on the H needle. It fires up every time with less than 3 pulls. It smokes off the line like it's supposed to, just not at the top end.

BTW, is there any issue with running these things for more than 30 min straight? Our group normally does tarmac auto-x style races where we literally run 30 min non stop around the course. I never check engine temps as I assumed they were made to take it. We have a long straight where there's a WOT pull for maybe 5 seconds.
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I have had a couple of customers bringing me equipment that they have replaced the original carbs with the clones found on amazon/ebay, the standard Walbro carb setting often do not even come close to having the correct running setting, often times the LSN is close to 1 1/4-1 1/2 turns out but the HSN can be as much as 2 1/2 - 3 turns out.. the stock settings set up by most engine/carb manufacturers are often a base setting, adjusted upon use, one persons motor may run great on HSN of 1 1/2 another at 1 3/4, even changing oil fuel ratio can make a difference, more oil = leaner fuel/air mixture..
 
You can tune your carb with a new plug if you want to get a good baseline. After you've broken in your motor, run her as you normally would at your "stock" carb settings for about 10-15 minutes. Kill the engine and pull the plug. If it's a chocolate color, it's good. If it's white-ish or ashy, you're too lean. If it's dark and wet, too rich. Make sure you kill the motor right after coming off the throttle. If you let it idle, the case will load up and give a richer reading than normal running conditions.

There is a diminishing return here. Subsequent plug readings will have lower accuracy after a point, but can still give you a basic understanding of where your engine is sitting, tune wise. If the plug is white-ish, you're too lean. That's the big take away.

Bryan K. said:
BTW, is there any issue with running these things for more than 30 min straight?
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You should be able to run your engine for hours on end without any issues so long as you have the tune right.
 
You have something seriously mechanical causing blown top ends. I doubt dirt as dirt usually causes siezed crank bearings first, followed by excessively scuffed piston skirts. Every piston failure offers clues about exactly what type of failure occured. We need more detailed pics of the complete piston , the piston crown, and the cylinder. Just a pic of the piston through the port is not enough.
 
Bryan K. said:
I should have mentioned that I also have an HPI Baja which I bought used. The motor looks old and I have no clue what it is. It pulls hard so it must be at least a 26cc CY with a 668 carb. I've run about 8 tanks through it now without any issues using the same gas/oil mix that I've been using on the DBXL. I don't think my gas/oil mix is the issue. I measure all my mixes uses that ALM mixing bottle and I make sure I'm precise with it. I notice my Baja smokes at WOT in the top end while my DBXL doesn't. It could just be blow by from the old baja motor, but still seemed suspicious to me. Maybe the 997 carb isn't working properly on the H needle. It fires up every time with less than 3 pulls. It smokes off the line like it's supposed to, just not at the top end.

BTW, is there any issue with running these things for more than 30 min straight? Our group normally does tarmac auto-x style races where we literally run 30 min non stop around the course. I never check engine temps as I assumed they were made to take it. We have a long straight where there's a WOT pull for maybe 5 seconds.
Click to expand...
Just was rereading this post and noticed you mentioned about blow by, as a two stroke used the piston to force the air fuel mix into the cylinder you would notice blow by like in a 4 stroke, when the ring gets to that point of wear, normally performance starts to suffer and compression starts slacking off. I think the smoke at WOT your seeing is just a good carb setting. A tad ritch.

Have you had a chance to pop any of your old top ends off and get a better look at them? Very keen to see what's going on inside so we may be able to give you better advice on the issues you've been having.
 
Attached a bunch of pics. Sorry for the delay, I couldn't find an extended T27 torx bit required to remove the head until now.

Oddly enough I had a 30cc piston and 4 bolt head laying around and decided for fun to see if I could bolt it onto the 2 bolt 29cc bottom end. It fit perfectly fine and the piston moves smoothly with lots of compression. I used the 2 bolt gasket and it seals just fine. Any reason why this wouldn't work? I wasn't able to find any info on people attempting this.

BTW, as for the condition of the damaged piston and head, I noticed the spring clip on one side of the piston was missing. Do you think maybe it flew off and caused all that damage? It honestly does't look like a lean condition failure. It literally looks like a foreign object got grinded up in there. Anyways, opinions please? I'm not engine expert.
 

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