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DRP: Derbi Reactivation Project

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toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Exxon Valdez

Post by toratora » Fri Oct 02, 2015 7:39 pm

I've got the squish about as close as I'm going to get it with this setup. I think it's a bit much, but it will have to do until the proper head shows up. :)

I've also got the leaks stopped. I did break down and employ some sealant. :) I will probably get the rest of the engine together today. :D

I did notice that the clutch basket seemed loose. I have a basket off the Senda (I have a Senda project too) that isn't loose, but it's not on the engine. So I opened up the 45mm stroke engine's clutch case to see if it is indeed how the baskets sit when installed, and sure enough that one was loose too.

With the clutch cover off I did discover more evidence that it could be a bad main seal on that engine. Check out all the junk in the oil. I wont really know for sure though unless I do more tests. I'm considering putting on a top end to do a pressure test, but I'm fairly certain that I'm going to have to split the cases on this engine.

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Mystery Bus

Post by toratora » Fri Oct 02, 2015 9:39 pm

I can't believe how much good data I'm collecting with the leak down tester action.

Tonight I got the the Monza engine out for a check. It seized on a ride a few Sundays ago. The entire time I've had this bike I've never been able to get it to run right. Well there's a big wow, and I found it with the leak tester.

Here's the plug. It looks okay.

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The bottom of the piston. There's some discoloration, but it's not that burnt.

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The piston broke up at the ring pin, but the seize wasn't that bad. I will probably be able to clean it out with some muriatic acid.

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When I did the leak test I found three places where it was leaking. On top where the carb is just below the cylinder at the case split, and in the same place below at the case split. The third one, well...

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Check out this pin hole. How could something like this even happen?

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The previous owner did quite a bodge job on the cases. Two of the case screws have been exposed to the crank case. I've always thought this was the big issue with this engine, and it is a problem. If I don't put sealant all over these bolts (yeah stock they are screws, but I replaced them with bolts). But even putting sealant on the bolts didn't halt the problem. But it didn't make any sense.

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Hmm...I don't have a good photo, but it turns out that the previous owner did some sort of epoxy JB action to deal with going through the cases. This bondo job seems to have failed enough to create a crack or something, and developed a leak. As we can see from the bubble evidence. Now I have to figure out how to fix it. I'm thinking sourcing new cases might be the best way to go, rather than trying to repair the mess left over from the previous owner.

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Setting the Proper

Post by toratora » Sat Oct 03, 2015 9:39 pm

It's one thing to blow up a kit because you are pushing it to win a race, or some such, but it totally sucks to lose it due to some lame ass air leak. The Track Bike is next on the list to get tested, but it's over at Ed's so it will have to wait. I suspect, with the exception of the intake manifold which I know is suspect, that the PPMPR engine doesn't have any leaks. I say this because it's been a very stable good running engine. :P

I am also pretty convinced that there's going to be a MyChron42T. This will mean that the plastics will have to wait even longer to be ordered, but I really want to make sure things are running properly. And it looks like getting the Koso two stroke lambda sensor bung with one of the lambda sensor kits is in order too. It doesn't look like there's a lambda unit available for the MyChron, but the one lambda sensor can send out data, and maybe that data could be sent to the MyChron for tracking.

With that setup one could then have EGT, CHT/H2O, and lambda tracking. Those three data points would give you some pretty serious information. I'm going to have to source a good MyChron dealer. There's a kart shop in SJ called Cambrian. They sell the MyChron, and might be a good source--but damn it this stuff is expensive. I've also seen them on eBay, and Summit has them.
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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Enter the Dragon

Post by toratora » Sun Oct 04, 2015 9:39 pm

I think I'm suffering sticker shock with the MyChron. When you start adding up all the little bits it could quickly add up to over a grand! This has got me thinking that maybe there's some other possibility. When it was a $300 device it looked quite attractive. :P

I'm coming to the point that the engine is going to be complete.

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One issue that's been bugging me is the stator plate for the Puch when placed on the Derbi there's no room to move it. The timing must be set by placing the flywheel on the crank. Not very friendly. I'm going to have to see if HPI makes a plate for the Derbi Euro2 engine.

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I picked up a Polini PWK for the moped, but now since it's in limbo I may just put the carb on this engine.

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Sensors Working Overtime

Post by toratora » Mon Oct 05, 2015 3:39 pm

Yeah the programable box is on the list, but the list is long, and it takes a long time for things on the list to appear. :P

I went ahead and did the install based on the the online HPI docs. The Derbi engine turns counter clockwise, so the mark on the left of the stator is the one that gets lined up with the mark on the rotor, once you set the crank such that the piston is 2mm below TDC.

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The nice thing is I'm getting to the point where I'll get to play with some nice toys like the Jolly Moto. I picked this up off of eBay a long time ago. I don't know how it will like running with a kit this big though. Ideally I would get a more appropriate Jolly Moto, but well that's just not going to happen any time soon. This one had been boogered up a little bit, but it should be fine.

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Another thing I found in the stash is the Daytona temp meter. I don't have the sensor for it though. I tried the Koso sensor since it has the same connector, but it seems to be incompatible. The nice thing though is that it came with an adaptor. Maybe the TTO Trail Tech sensor will match up with it. ;)

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Scientific Degrees

Post by toratora » Mon Oct 05, 2015 5:39 pm

My moped buddy Tyler put together a neat little calculator for converting mm from TDC to degrees of rotation. You need to know the stroke, and con rod length. For the Derbi type engines that's 40mm, and 90mm.

The docs for the HPI suggest 2mm before TCD, which is roughly 23.5° of rotation. This information becomes handy if you decide to check your mechanical timing settings with a timing light. Tyler suggests doing so with the HPI mini rotor because he's seen the markings on the flywheel to be way off.
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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: The Fucking Ignition, Al!

Post by toratora » Mon Oct 05, 2015 9:39 pm

Okay, an area where I have much learning to do is with the ignition. I understand the basic concepts, but that's not enough for really tuning this stuff to the level that I want to achieve. Like Matt suggested previously I need to get the programable version of the HPI kit. That's actually one of the reasons I've invested so heavily in HPI--you can program it. ;)

Here's the ignition curve of the HPI.
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The stock setup is to have the Derbi engine set to about 23° BTDC (before top dead center). But how does this compare to where the engine gets on the pipe, and peak power, because isn't that where you want to set up the curve to function? Well I don't have the data on this engine to know. This is a new combination for me. But I do have what I ran previously on this bike. Norcal Cycles does an annual dyno day. It's a blast. lots of different bikes show up. I'm of course the only goof ball to show up with a two stroke. :lol:

Here's what the 45mm stroked Airsal Xtreme did with a 24mm PWK, Metrakit ProRace, and the HPI set at 2mm BTDC. From this chart, and by looking at the curve chart we can read that at peak power ~13.5K the bike had ~5° of advance, and at ~9K where the bike starts getting on the pipe there was ~15° of advance. Which my friend Tyler should be ~16° of advance when the bike gets on the pipe, and 20° at about a 1K idle.

Tyler also mentioned that the HPI mini rotors that he's worked with should be checked with a timing light, because he's found that the markings aren't particularly accurate. So all of these readings should be somewhat suspect, because I set everything mechanically, and didn't run it with a timing light. I didn't know that the mini rotor had this feature. :eek:

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And because you'll want some sexy, here's what the bike looked like that day.

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And what the ignition was set to on the bike.

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2mm BDTC

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Interesting how the older version of the HPI had a different plate.

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Strobo Lightsu

Post by toratora » Tue Oct 06, 2015 3:39 pm

Tyler told me that the markings on the HPI 2Ten mini rotor are not dependable, and that it's best to set it mechanically at first, and then check it with a timing light. Now I have the engine assembled, but not installed so I haven't checked it with a light, but I've been reading about lights. This is sort of bad news. Our engines don't even act as if their are on until 5, 6, or 7K. The 45mm stroked engine didn't get on the pipe until 9K, and it peaked at around 13.5K.

Looking at the timing lights even the MSD $220 timing light is only rated to 5K rpm. Which is to say you can check the idle, but you are not going to be able to accurately check the advanced timing.

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Adjust to Fit

Post by toratora » Wed Oct 07, 2015 3:39 pm

With the suggested settings, and the original (red) curve the bike would be at around 5° advanced at peak power (13.5K rpm). My understandings is that with a stroker less advanced creates hotter gasses sent into the pipe, which because they are hotter they travel faster, matching the higher RPM, producing a better "super charging" effect. If I'm understanding you correctly, and reading the chart correctly, wouldn't I be seeing about 17° at 13.5K rpm? Shouldn't it be less advanced near the top for the hotter gasses?

Oh and sadly I can't adjust the stator. It's on where it's on. Any adjustments have to be made by taking off the flywheel, and placing it in a new position. Which is a real pain in the ass, and difficult to be precise. I've asked Willy if they have a more appropriate plate for the Derbi, since I'm currently using the Puch plate.

I'm currently working on the chassis. Mostly just cleaning parts. It's a lot of work to clean this stuff. The really great news though is I finally found the box with the chain adjusters. :D I was really worried about not finding those suckers, because I've never seen them on the eBay, and to order them could take 6 to 8 weeks! :eek:

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User avatar
toratora
Posts: 3153
Joined: Wed Oct 11, 2017 1:05 am
Location: San Francisco
Replica: Derbi GPR
Cagiva Mito
Cobra CX65
Aprilia RS50
x 1734
x 1970
Contact:

DRP: Spick and Span

Post by toratora » Fri Oct 09, 2015 3:39 pm

First things first, got to get the bike back on the road. :lol: Man does it take forever to clean this stuff.

I did a bit of fiddling around. I'm going to be running 2003 front farings, and the stock tail section. Just parts of it for now. I have some plans, but it's going to take a while to realize. I also think I'm going to forgo the stock air box too.

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