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Post by Lucass2T on Aug 27, 2022 13:58:33 GMT -5
You 100% sure its nothing ignition related? Did you try different gaps?
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sinfull
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Post by sinfull on Aug 27, 2022 15:16:12 GMT -5
Definitely worth having a look at the cylinder. Easy enough to look and get a idea of what is going on in there.
Other suggestion is to use the most dead nuts consistent carb you have, old faithful. Should be a easy swap, even if you have to make a extension to the intake and see if it really is a carb issue or something else.
Thought is if old faithful can't get it right then it is something else going on.
We all have that 1 carb stashed away that ran on every build and know we can get a decent tune on in like 5 minutes
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Post by 90GTVert on Aug 27, 2022 17:00:50 GMT -5
I did 2 compression tests. 1 with the Snap-On gauge and 1 with the Actron gauge. Both using the same adapter, because the Actron's wouldn't seal. Snap-On says 155-160psi. Actron says 135-140psi. I never checked compression when it was fresh. Regardless, I already know it runs decent when not heavy on the throttle so I'm not even totally sure why I checked now. The engine is out now. That's as far as I got. Question for folks that are used to Aerox wheels... Do you take the wheel off to remove the rear brake caliper? I figured the rear brake caliper would be easy enough. Just remove 2 bolts and take it off and the whole engine and wheel can come out. Won't fit out of the wheel. Just wondering if it's par for the course or maybe some brake calipers do fit out. Link to what I'm using below. It almost fits out, but I'd have to scratch the powder coat if it would come out. Not a big deal, but it would save time for future swaps if the wheel and adapter could stay on. www.scootertuning.ca/en/brakes/34051-rear-brake-caliper-red-aerox-nitro-4051272011160.htmlSide note; I was pretty happy that the impact driver could remove the adapter nut (torqued to 89lb-ft). I have an air impact wrench, but these little things are surprisingly capable. You 100% sure its nothing ignition related? Did you try different gaps? I'm not 100% sure of anything ATM. I haven't tried reducing the gap to see if it clears up. Definitely worth having a look at the cylinder. Easy enough to look and get a idea of what is going on in there. Other suggestion is to use the most dead nuts consistent carb you have, old faithful. Should be a easy swap, even if you have to make a extension to the intake and see if it really is a carb issue or something else. Thought is if old faithful can't get it right then it is something else going on. We all have that 1 carb stashed away that ran on every build and know we can get a decent tune on in like 5 minutes The 25mm Dell has been a good carb for me, but I guess my old faithful would be a 21mm PHBG. Not adapting that to the RC1 and I've also went through some sort of tuning woes with any carb I've ever used much. I think with 2 carbs doing this, something else is up. If it were stuck rich at lower throttle too, I'd be worried more about the canted carbs.
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Post by aeroxbud on Aug 27, 2022 18:43:44 GMT -5
Yes you have to take the wheel off to get the clearance for the caliper to come off. You would think as they use a different caliper to the front wheel, you wouldn't. But no.
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sinfull
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Post by sinfull on Aug 28, 2022 3:18:44 GMT -5
So you have good compression, you have spark and it runs, your timing and ignition are set up correctly, no vacuum leaks,then that leaves fuel.
Has to be something really small that you are not seeing yet. Or it is the carb angle that is messing you up. Can't really think of anything carb related that you have not done.
Can't imagine that you would set up a carb any different depending on the angle, I mean it is just a carb, venturi opens, sucks fuel up a hole and down the throat.
Watching this with interest because when you figure it out and tell us what the problem was we can all say WHAT THE, THAT'S CRAZY THAT IT DID THAT lol
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Post by captincvmn on Aug 28, 2022 9:36:38 GMT -5
I thought my previous engine was spark, mixture, everything except the piston rings which were gummed into the ring lands. I chased my tail for two weeks being stubborn and thinking I knew what it might be.
You’ll get it Brent. Proper amounts of mixture, compression, spark timing and it’ll go. It’s just a matter of time until this engine submits to your will.
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Post by 90GTVert on Aug 28, 2022 10:16:38 GMT -5
I cleaned the engine up a bit this morning and then did a couple of checks.
I wanted to do a leak test before anything was disassembled so I would know for sure if it was sealing while this happened. It passed a 6 psi test.
I looked into the exhaust port while setting it up for the leak test. The piston looked pretty good from there.
I removed the intake and checked the reeds. The reeds look brand new. They sit nicely up against the block and there aren't rough edges.
I almost hate to take the top end apart now, but I did have very dark coolant. Could possibly be an o-ring issue I suppose. Other engines have been sealed according to a leak test and then showed signs of combustion entering the coolant. On the TPR it would leak coolant into the cylinder I believe and then mess up the edges of the piston crown. Not seeing that just from the side in the exhaust port though. I've got, I think, about 450 miles on it right now. Some would say it's time for at least a ring in that time span for a race build, so I don't think it's a total loss pulling it apart just to check. Plus, it's me. If I decide to put it back without checking you can guarantee that weeks of aggravation later I'll find the problem was a ring or o-ring.
Before I take the top end off, I think I'll put an indicator on it and just make sure the marks on the MVT still align as they were initially set.
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Post by oldgeek on Aug 28, 2022 12:18:07 GMT -5
........Before I take the top end off, I think I'll put an indicator on it and just make sure the marks on the MVT still align as they were initially set. It may save you from pulling the top end off. Timing would not have to move much to cause you issues.
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Post by 90GTVert on Aug 28, 2022 13:29:51 GMT -5
The timing marks still align at 0.35mm BTDC as set when installed.
Cylinder is off. Looks really good to me. I'm in the process of cleaning everything. Eventually I'll measure the piston and bore and the ring end gap. As of now, I'm thinking the engine is fine. Probably wasted my time, but it doesn't really hurt my feelings to get an idea of how the engine is wearing.
It may be something like swapping a CDI. I've had scoots act pretty weird from a bad CDI, but never in the middle of carb tuning before.
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pewpew
Scoot Enthusiast
Posts: 254
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Post by pewpew on Aug 28, 2022 18:03:43 GMT -5
I did 2 compression tests. 1 with the Snap-On gauge and 1 with the Actron gauge. Both using the same adapter, because the Actron's wouldn't seal. Snap-On says 155-160psi. Actron says 135-140psi. I never checked compression when it was fresh. Regardless, I already know it runs decent when not heavy on the throttle so I'm not even totally sure why I checked now. The engine is out now. That's as far as I got. Question for folks that are used to Aerox wheels... Do you take the wheel off to remove the rear brake caliper? I figured the rear brake caliper would be easy enough. Just remove 2 bolts and take it off and the whole engine and wheel can come out. Won't fit out of the wheel. Just wondering if it's par for the course or maybe some brake calipers do fit out. Link to what I'm using below. It almost fits out, but I'd have to scratch the powder coat if it would come out. Not a big deal, but it would save time for future swaps if the wheel and adapter could stay on. www.scootertuning.ca/en/brakes/34051-rear-brake-caliper-red-aerox-nitro-4051272011160.htmlSide note; I was pretty happy that the impact driver could remove the adapter nut (torqued to 89lb-ft). I have an air impact wrench, but these little things are surprisingly capable. You 100% sure its nothing ignition related? Did you try different gaps? I'm not 100% sure of anything ATM. I haven't tried reducing the gap to see if it clears up. Definitely worth having a look at the cylinder. Easy enough to look and get a idea of what is going on in there. Other suggestion is to use the most dead nuts consistent carb you have, old faithful. Should be a easy swap, even if you have to make a extension to the intake and see if it really is a carb issue or something else. Thought is if old faithful can't get it right then it is something else going on. We all have that 1 carb stashed away that ran on every build and know we can get a decent tune on in like 5 minutes The 25mm Dell has been a good carb for me, but I guess my old faithful would be a 21mm PHBG. Not adapting that to the RC1 and I've also went through some sort of tuning woes with any carb I've ever used much. I think with 2 carbs doing this, something else is up. If it were stuck rich at lower throttle too, I'd be worried more about the canted carbs. No need to take the wheel off, you just have to press the piston in first by pushing the caliper to the rotor. Then it comes out
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Post by 90GTVert on Aug 29, 2022 13:15:02 GMT -5
I cleaned everything and then it seemed like the piston ring didn't move as free as it should. I took the ring out and cleaned it and the groove. Better, but I still wasn't sure about it. I tried to measure side clearance with feelers and 0.0015" kinda fit. It needed pressure to squeeze in there and it's such a thin piece. I used 2 feelers to measure the ring groove and I got 0.033". I measured the ring a little over 0.031", so 0.0015" is close enough. Common spec seems to be 0.0015-0.003", with a wider range of 0.001-0.004" accepted by some. Either way, mine should be fine. I may be a but paranoid about the ring due to my expectations prior to disassembly. It was certainly moving freely with oil residue present. The ring end gap is about 0.010". The spec is 0.006" and that's where it was initially set. I have a new ring here, but based on that I wouldn't really need to swap it out. The piston was measured to be 2.0444" or 51.928mm brand new. That now measures 2.0429" or 51.89mm, so it "shrunk" 0.0015" or 0.038mm in 469 miles. The bore ranged from 2.0472-2.0478" or 51.999-52.014mm brand new. Now I get 2.0474-2.0478" or 52.004-52.014mm, so that's as much as 0.0002" or 0.005mm larger. The top and below port measurements were 0.0002" larger and the bottom above the cutouts came out the same as new by my measuring. Originally, the piston to cylinder clearance ranged from 0.0028"/0.071mm to 0.0034"/0.086mm. I thought it was a bit large to begin with, based on Malossi's spec of 0.048-0.056mm (0.0019-0.0022"), but others assured me that it's common for Malossi kits to have more clearance than specified. Now clearance ranges from 0.0045-0.0049" or 0.114-0.124mm. Definitely more than I would like to have, but I'm not changing the piston just yet. I will probably order one. ScooterTuning doesn't seem to carry them so I'll probably see if I can get a larger size. If I wanted to meet their spec, I'd need a C piston. If I can find one, I may go that way. A or B would put me closer to original clearances. Not sure if I should go all the way to C to try to match their spec or just look for a B. The things wear so quickly that C seems to make more sense to me as long as it's not too snug to start. EDIT : Ordered 3416448.C0 (C Piston) for $85 from Latvian seller on eBay. Otherwise it looked like a piston was going to be more like $130. G-Force does carry them in the US, but I hope to not need this sooner than the 2 weeks estimated anyway. Long story made short; I still don't see any reason that the engine condition should be giving me high throttle sputters and I don't even think I'm going to bother with the new piston ring. Sorta off-topic... I picked up Scotch Brite scouring pads that are non-scratch for non-stick and stuff. ( These : amzn.to/3Az4QLS ) My cleanup is done now, but I'm curious to try them on an old cylinder or something and see if maybe they would provide a quick cleanup without scuffing anything. I use a plastic razor scraper and carb cleaner followed by finer Scotch Brite pads as needed now and that works OK. Would be kinda nice if something that you can get at the grocery store would do the job, after looking at prices for the others online today.
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Post by 90GTVert on Aug 30, 2022 18:03:39 GMT -5
I got the engine back together, leak tested and back in today. I swapped back to the VHST, assuming my issue is elsewhere. I left the other cable tied up on the scoot just in case I end up switching carbs around again though. I put a 145 MJ in there and headed out for a test ride as a storm was rolling in.
I just went into town and back (5-6 miles). It ran mostly clean WOT going to town. Did fine ripping through town trying to make my lap before the storm hit. Coming out of town I got up to roughly 70MPH before braking so I didn't run into traffic. I think I had a few "misses" during WOT spurts, but it mostly seemed OK. It poured about 2 minutes after I got home, which is why I didn't keep going. I really wanted to do some more WOT bursts, but didn't feel like getting drenched and figured I could cause myself more trouble with the pod filter and heavy rain anyway.
I mentioned that the coolant was dark when I took the engine out. There was sorta soot in there. I've seen similar stuff with my other LC engines. I assume it to be basically soot or combustion remnants of some sort. I thought maybe it was leftover from past builds and not flushing the system. Now I'm wondering if I did have a bad seal somewhere. I didn't really change anything other than the gasket and o-ring kit.
I'll get some pics up at some point, but to me it looked like it was sealing from the marks on the head and cylinder. The piston looked good. It would seem to me that it would have had to loose pressure under the heaviest load and have combustion pushing past to put soot in the coolant (if that's what it was). I could imagine that pressure loss or changes could cause it to act funny. I may test it tomorrow and find that this ride was just a fluke and it runs terrible again.
I've got plain distilled water in it now. I'll do some test runs and then drain and refill it.
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Post by 90GTVert on Aug 30, 2022 18:24:11 GMT -5
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Post by aeroxbud on Aug 31, 2022 4:34:10 GMT -5
The cylinder seems to be holding up very well. Much better than the TPR.
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Post by captincvmn on Aug 31, 2022 5:09:47 GMT -5
Dollars per durability it should hold up forever
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