|
|
Post by broyager on Apr 13, 2023 16:16:59 GMT -5
The holes for the head are pretty tight, but cylinder holes are bigger and haven't changed. I have made a mistake, decided that the naraku kit / piston had gone out of spec, and bought a malossi sport..  The noise still remains with malossi installed though, so I haven't run it yet. I think this noise is the piston rotating in the cylinder and clacking the rings against the little ring pins. It is quite pronounced with the naraku, as the rings are quite loose in their slots, and less so with the malossi, the rings are much wider, and fit more snuggly, but there is still movement. I think this is normal, but there must be some twisting going on with the conrod maybe. Can only hear it with spark plug installed / compression exists. Conrod looks straight, and it seems to move straight without twisting, but maybe the eye can't pick that stuff up. Either that or this sound is totally normal....
Interestingly, the malossi sport with mhr head, and a single base gasket (0.46mm) comes out at a whopping 1.5mm of squish. It needs a base gasket, plus another 0.2 or 0.3mm actually, to get the piston to the bottom of the exhaust port on bdc. So I'd need to be looking at taking 0.5 - 0.7mm off the top of the cylinder in any case to get anything like a decent squish.
Also the ports are all bigger on the naraku, including the one on the bottom of the piston, and the cooling fins on the naraku cylinder are quite a bit bigger, which might be why it runs a lot cooler than others have experienced.
Anyone have any ideas?
I'm thinking I have to throw more money at it... and replace the crankshaft..
|
|
Kaos
Scoot Enthusiast
Posts: 185
|
Post by Kaos on Apr 13, 2023 17:14:19 GMT -5
The holes for the head are pretty tight, but cylinder holes are bigger and haven't changed. I have made a mistake, decided that the naraku kit / piston had gone out of spec, and bought a malossi sport.. The noise still remains with malossi installed though, so I haven't run it yet. I think this noise is the piston rotating in the cylinder and clacking the rings against the little ring pins. It is quite pronounced with the naraku, as the rings are quite loose in their slots, and less so with the malossi, the rings are much wider, and fit more snuggly, but there is still movement. I think this is normal, but there must be some twisting going on with the conrod maybe. Can only hear it with spark plug installed / compression exists. Conrod looks straight, and it seems to move straight without twisting, but maybe the eye can't pick that stuff up. Either that or this sound is totally normal....
Interestingly, the malossi sport with mhr head, and a single base gasket (0.46mm) comes out at a whopping 1.5mm of squish. It needs a base gasket, plus another 0.2 or 0.3mm actually, to get the piston to the bottom of the exhaust port on bdc. So I'd need to be looking at taking 0.5 - 0.7mm off the top of the cylinder in any case to get anything like a decent squish.
Also the ports are all bigger on the naraku, including the one on the bottom of the piston, and the cooling fins on the naraku cylinder are quite a bit bigger, which might be why it runs a lot cooler than others have experienced.
Anyone have any ideas?
I'm thinking I have to throw more money at it... and replace the crankshaft..
Is the noise that clack at the end??? You shouldn't be able to hear ring rotation if they're installed properly. You should only hear the sound of sucking air in and a whoomph of it being pushed back out. No clicks, clacks, or taps. |
|
|
|
Post by broyager on Apr 13, 2023 20:39:19 GMT -5
Yep, that's what I figured, but still am not able to confirm what this noise is.
I've just put it back together with the naraku cylinder, and I realize now that I'm turning the engine backwards...:/ so this clack might not be the one I'm hearing when it's running...
There is some slight grinding when I push the conrod to one side, and rotate the engine...
It's possible that some debris, from when I seized the 50cc cylinder (broken C clip), did make it down into the crank, or maybe that bottom bearing is just worn out...
|
|
Kaos
Scoot Enthusiast
Posts: 185
|
Post by Kaos on Apr 13, 2023 21:24:36 GMT -5
Yeah, could be either of those. Make sure that's not the connecting rod hitting the bottom of the cylinder skirt either.
|
|
|
|
Post by broyager on Apr 14, 2023 1:55:48 GMT -5
Good call, though I haven't seen any witness marks which could indicate that. It's fucked... just went out for a ride, goes great, but sounds like it's about to fall apart.
These are new rings, but that shouldn't create this noise.
|
|
|
|
Post by aeroxbud on Apr 14, 2023 4:54:56 GMT -5
It must be something to do with the crank if it's doing it on both cylinders.
Does it make the clicking noise when you turn the crank without the cylinder on?
|
|
|
|
Post by broyager on Apr 14, 2023 6:35:19 GMT -5
Not that I can tell, only with cylinder installed and head tightened.
There is maybe a very quiet click with no variator and piston etc installed, holding the conrod of course, so it's not banging on the case opening.
Conrod has just a little side to side play, maybe a 1mm or so side to side at the small end, and there is a slight notchiness side to side at the big end. The crank itself doesn't move at all in any other direction that it's supposed to. Gap between the big end of the conrod and the sides is well within spec.
Maybe the conrod is distorted slightly, and I just can't see it.
It's been through a seize as above (ingested circlip) and a soft seize which has been remedied.
|
|
Kaos
Scoot Enthusiast
Posts: 185
|
Post by Kaos on Apr 14, 2023 10:00:24 GMT -5
Not that I can tell, only with cylinder installed and head tightened. There is maybe a very quiet click with no variator and piston etc installed, holding the conrod of course, so it's not banging on the case opening. Conrod has just a little side to side play, maybe a 1mm or so side to side at the small end, and there is a slight notchiness side to side at the big end. The crank itself doesn't move at all in any other direction that it's supposed to. Gap between the big end of the conrod and the sides is well within spec. Maybe the conrod is distorted slightly, and I just can't see it. It's been through a seize as above (ingested circlip) and a soft seize which has been remedied. Dang dude, ballsey to ride it sounding like that  Could absolutely be a bent rod. A seize puts a lot of stress on the rod when everything comes to a halt very suddenly. Either way, sounds like you're in for more work figuring it out for sure... |
|
|
|
Post by broyager on Apr 15, 2023 1:49:29 GMT -5
I think I'm getting closer, but am going through base gaskets... When I push the conrod to the left, there is definitely some slight binding, at TDC and BDC, and I think this is causing piston slap at those points. It seems like the rings are causing some of that noise too, rattling inside the lands when the piston changes direction. I pulled the oil pump up to eliminate that but it didn't change anything. There is a small tick with nothing connected, and I think this is coming from the flywheel / generator, but this is very light / high, so is separate to the main noise. So I'm still looking at a new crankshaft unfortunately, the minimum I can get the basic athena pgo crank, bearings, gasket, flywheel puller, and some new studs shipped to NZ is $375NZD. (from speed-line.com) I've picked up that the full circle 'race' cranks will not fit without taking some material from the inside of the case, can anyone corroborate that? In the mean time, as this is my daily, I will try to bend the conrod to the left a little, with the idea being it gets centered more to the right when the cylinder is on, and keep it away from that bind on the left.
|
|
|
|
Post by aeroxbud on Apr 15, 2023 5:29:11 GMT -5
Did you check the standard ring end gap before you installed them?
When I bent my crank, it was obvious. It sounded like a diesel!😬
|
|
|
|
Post by broyager on Apr 15, 2023 5:35:05 GMT -5
Yep rings are new on the naraku, and come standard at about 0.011" from memory, wider than I thought they should be, but inside spec and rings on the Malossi were 0.008" and 0.010"
|
|
|
|
Post by John Kiniston on Apr 15, 2023 8:31:32 GMT -5
Any shops near you that can true the crank you have instead of replacing it?
I’ve had all sorts of things done to cranks, weight reduction, conrod swaps, and balancing.
|
|
|
|
Post by repherence2 on Apr 15, 2023 16:23:36 GMT -5
are you the one that converted it from 50cc (40mm) to 70cc (47mm) bore?
...if so, did you use a hammer to persuade the wrist pin to remove it?
last question, if you are running JOG/minarelli spec bore kits (Naraku/Malossi), why are u running a bPr7hs and not just a br7hs? why are you running a "Projected" plug on a JOG/minarelli head? i did a g00gle search and i found that Genuine even calls out for a bPr7hs. i tried to search for pictures of the stock Buddy50 head but could not find any. so, my deduction is that the stock Buddy50 head uses a "Projected" plug. how ever, i do not see how you run a BPR7HS on a JOG kit head. i run Chinarelli stuff, but when i would buy my parts at Motosource, the shop owner told me only to run the BR_HS plugs and not the BPR_HS plugs, JOG's, REXY's, and Chinarelli's did not use the P plugs.
i say, try a BR8HS plug. it is a $4 part, and see if that makes a difference. the way i see it from reading your thread, your jetting is not tuned well at this point. the owner of Motosource told me to run BR8HS plugs while was tuning. he told me to switch to BR7HS plugs when i got the carb jetting in good tune, and then fine tune pilot/needle/main jet from there.
|
|
|
|
Post by broyager on Apr 15, 2023 20:28:15 GMT -5
Hi yes, and no the wrist pin is or was not seized in the piston.
Afaik the r is just for resistor, which I think helps smooth the current, or stops it from getting to other parts in the electrics. But that's just my afaik. It's the standard length plug, and would hit the piston crown if I used an extended one. Squish is 0.71mm so not much room in there.
I have tried an r8hs, but this was when I had the main up a few sizes, and it was tending to foul the plug. I'm finding that because the cylinder seems to run cooler than most, it needs the hotter plug to help burn mixture. I'm still slightly rich, but am happy with where it's at, and the plug colour is just on the rich side of ideal.
|
|
|
|
Post by broyager on Apr 17, 2023 1:22:42 GMT -5
Another question, should there be a lump in the rotation of a crank which isn't connected to anything, or should it be smooth? Oil pump is still connected in this example. Lumps are BDC TDC pretty much
I have a solution in play, a complete crankcase from a PMX 50 for $90NZD. The gears might be taller... I realize now, but I can always just put some lighter weights in. i have some 5g's rollers in good nick. Or is it the other way around? PMX has the 12" wheels I think?
Still riding it nervously, the clack seems to be changing into a lighter tick... so.. who knows. I know that the small bearing, wrist and clips are all new, and it's not overheating at all so, will take my chances for now...
|
|
