Derbi pp to cyl reed

My derbi stunk up the garage like gas all the fucking time. Stupid ass sha leaked gas all over the engine, tried a few things to fix but if it's not leaking from the bowl, it'll leak from the filter side. I cannot stand the blowback with piston port either, that's part of the gas stink as well.

The derbi stock jug is so nice that I wanted to make an adaptor to run reeds. Was going to do a V reed, but I didn't have enough billet to fit them, so I made an adaptor for some vertical minarelli jog flat reeds I had. Bolts on, and then I'll just make an intake and port it.

Don't want to make it rev to the moon, just want it to be a grunty fun beast that doesn't stink up my garage.

Already welded the decomp, such a nice head.

Adaptor looks giant, but it's cut inside for flow, not a giant cavern like your mom

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Re: Derbi pp to cyl reed

No derbi experience here...but that looks neat.

Re: Derbi pp to cyl reed

looks like fun

fabbed up plate steel wouldn't be a bad program either. if you're not scared to cut off those top fins... i dunno what it is that holds more people back from doing this.

i've tried a couple times to cast a reed adapter but it has ended in total shame and failure. as usual i'm doing it way harder than i need to.

Re: Derbi pp to cyl reed

Did the rest of the porting today, and cut the welded head, had a little contamination so there's some pinholes in the welds. I'll redo the head at some point with better prep next time, but it's good enough to run now.

Re: Derbi pp to cyl reed

Weird can't upload pics

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Re: Derbi pp to cyl reed

I couldn’t earlier tooooo

Re: Derbi pp to cyl reed

I cant wait to see this crammed into the frame

Re: Derbi pp to cyl reed

Anonymous User /
scootertrash

I did the reach around technique,, I mean wrap around the reeds in a funnel shape. For Sachs mod.

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Re: Derbi pp to cyl reed

Got it done today, but have to wait til tomorrow to test.

The weld filling in the decomp area was porous, so I'll redo it some time, tapped the decomp valve hole anyways so fuck you lil hole ass bitch.

Ported it to be a fast bike but controllable. Hopefully it'll be a good time to ride

Like your mom

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Re: Derbi pp to cyl reed

I kinda fucked up the inside of the reed block so it's not pretty, don't have long endmills so I just hogged shit out. it'll work fine, I punched a hole thru the side and had to tig it closed. Haha who cares.

Maybe your mom

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Re: Derbi pp to cyl reed

That welded head is sucking.

The trapped oils in the aluminum makes it very challenging to weld. Especially deep in the chamber. So annoying. It makes welding on a flat surface or edge seem really easy.

The compression felt great by hand for 50cc, but when read it only read 90. I think the porosity in the chamber opened up the whole decomp tract to the combustion chamber making way too much volume when running, but turned by hand it still feels good. Idk.

The bike was running hot today during jetting. I think that head is the main thing screwing stuff up. I also gotta get a cdi on this, can't stand points.

Re: Derbi pp to cyl reed

yeah not just that, i welded up a whole batch of those years ago to machine them into hobbit heads- remember with those spacer bushings? this was like 8 years ago? anyhow even brand new they welded like total dogshit garbo. that casting is porous as fuck.

welding up decomps is one of the few things i've found alumiweld is better than tig. i bet you're gonna keep having air leaks from that shit.

Re: Derbi pp to cyl reed

Well, I kinda decided that it's better to use some treats credit for the treats 50cc derbi decompless head, mostly because I gotta stop fucking with mopeds cuz band stuff calls. My teddy bear band is getting ready to rock bro

Hooked it up and set timing and it's awfully impressive for a ported stock bore. I have to upgear and put a cdi on it, but I can see the potential. Painted an old fucked up airbox I had silver and pooped it right in. Haha I'll do a new bottle and make the holes more even cuz this one is kinda jacked.

Pics!

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Re: Derbi pp to cyl reed

And yeah I was gonna try -alumaweld, shoulda close the pinholes with it. Oh well, the new head is great and the rest of this mod was free so live and learn

Re: Derbi pp to cyl reed

I learned with adding material to variators that alumaweld is the shit.

Doesn't warp the pulley at all, tig gets things a lil too hot unless you take a lot of breaks.

I have to fix a variator soon that I cut too deep and made windows in it. I'm going to tack weld tig aluminum plate over the holes, then cover the whole thing in alumaweld then turn back down.

I did one awhile back and it holds up really well, better than the aluminum castings for sure.

Re: Derbi pp to cyl reed

I forgot to mention I'm running a 21phbg on this 50 and it loves it.

Doing 360 deg intake really allows so much flow thru the engine. Even without a massive exhaust port, it handles it fine. I think once I get a cdi on this it will be a lil monster

AND IT DONT FUCKING STANK LIKE GAS

Re: Derbi pp to cyl reed

yeah boiiii that sounds sick

you think even with the big porting it still has plenty of torques to pull single speed or is this variators only jams?

oh yeah i forgot treats is right down the street now... i'm thinking 'man its crazy how fast he gets shit done, even his treats show up same day.... '

Re: Derbi pp to cyl reed

I just did a treats reed on an e50 with my same porting but no timing change and the band was still super wide.

Very low clutch stall.

I was really impressed and actually surprised at how nuts the low rpm power was.

Pretty much adding boost ports and either cutting a big window in the piston and/or cutting out the center of the cyl intake skirt to the base makes a kind of open channel for the mix to flow into the cases, and up into the boost.

I fully expected it to be a very narrow power band but nope.

I do want to try a high rpm pipe with these lower timed cylinders to see if the wide band can translate up only due to the pipe.

Re: Derbi pp to cyl reed

Took this out on a final test run and its mostly awesome, needs a slightly more rich needle position.

Climbed the steepest longest hill I have and got to 340 at the top. It's just really snappy on the throttle. I love that.

Didn't have to change the variator tuning, it didn't give a fuck.

This porting technique rules

Re: Derbi pp to cyl reed

Anonymous User /
scootertrash

> JBOT Admin Wrote:

> -------------------------------------------------------

> I just did a treats reed on an e50 with my same porting but no timing

> change and the band was still super wide.

>

> Very low clutch stall.

>

> I was really impressed and actually surprised at how nuts the low rpm

> power was.

>

> Pretty much adding boost ports and either cutting a big window in the

> piston and/or cutting out the center of the cyl intake skirt to the base

> makes a kind of open channel for the mix to flow into the cases, and up

> into the boost.

>

I trim the boost plus the sides down to the base as well to juice it up at bdc.

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Re: Derbi pp to cyl reed

Me too ^^^

Re: Derbi pp to cyl reed

On 50s I take the boost all the way to the edge of the base, creating a tunnel where the skirt used to be to make the port. On a 70 there's not enough room to do much unless you cut the cases. This allows big mix into the cases whenever the engine needs it. Allows massive jetting and big powahhhhh

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Re: Derbi pp to cyl reed

Yeah, trimming the side skirts is good on some, gotta be careful with shorter stroke 50s like hobbits tho, they don't love losing the case stuffing. The derbi has 43mm stroke so it doesn't care as much.

My 50cc ported hobbit has not great idling and kinda slower throttle response because of a lil too much skirt grinding. I need to redo with another stock jug.

> Moore Burns & Payne Crematorium Wrote:

> -------------------------------------------------------

> > JBOT Admin Wrote:

>

> > -------------------------------------------------------

>

> > I just did a treats reed on an e50 with my same porting but no timing

>

> > change and the band was still super wide.

>

> >

>

> > Very low clutch stall.

>

> >

>

> > I was really impressed and actually surprised at how nuts the low rpm

>

> > power was.

>

> >

>

> > Pretty much adding boost ports and either cutting a big window in the

>

> > piston and/or cutting out the center of the cyl intake skirt to the

> base

>

> > makes a kind of open channel for the mix to flow into the cases, and

> up

>

> > into the boost.

>

> >

>

> I trim the boost plus the sides down to the base as well to juice it up

> at bdc.

> >

Re: Derbi pp to cyl reed

Was having problems with detonation and so I checked squish with the new head.

Lol like .6mm with a tiny combustion chamber.

Didn't need it that tight and didn't want to give up a standard timing for a lil extra compression so I bumped it out with a .8 head gasket. No more detonation. Now to lighten rollers a bit and blast boiiiii

Re: Derbi pp to cyl reed

This is cool.

Re: Derbi pp to cyl reed

Rode it the other day and it's just like a kitted bike. Amazing what extra power you can get by porting and reeding a pp cyl without adjusting timings.

Re: Derbi pp to cyl reed

should have this wrapped up in a couple days here

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if my figgerin' is right, it ought to be about the right thickness to act as a spacer on a ZA so i can run a polini intake with a bing on a stock cylinder

Re: Derbi pp to cyl reed

I just picked up a PP derbi and I've been trying to decide what mild reliable type shit to do. I might have to copy this. Can I ask why no decomp? Was it solely just to reshape the head or what?

Re: Derbi pp to cyl reed

I've never seen a combustion chamber with decomp that performed really well. They are ok, but a real combustion chamber makes lots of difference. When I first switched from a hobbit head to one I made with no decomp and a really good squishband, the swap just woke it up

Cool riser Graham. Just gotta port the shit out of the cyl to get the gains. The porting I did just sounds so brappy. BRAAAAP(edited)

Re: Derbi pp to cyl reed

The poorlini dream is alive and well!!!

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