Derbi Piston Port stuck at slow

OK, story time so you know whats going on.

Got a derbi- stock 30mph

Added Tomos Tecno Estoril and, 13mm SHA, upjetted- 36mph

Full rebuild- still 36mph (thats good)

Ported cylinder- 32mph, less torque, but can really wind out downhill and on flats.

65cc Parmakit- 36mph, same torque as stock, but still 36mph

I have played with an assortment of variator weights as well

I have jetted correctly, tried different timing and so on. I know people who have stock cylinder ones that are pretty fast, I have kitted quite a few bikes before, using 13mm SHA's and got ~45mph out of them, but I am at a loss with this bike. It just doesn't want to go faster.

Any ideas?

Re: Derbi Piston Port stuck at slow

#CrazyWayne™ rocks. #CrazyWayne /

Kevin Pierce (West Coast Mopeds) Wrote:

-------------------------------------------------------

> OK, story time so you know whats going on.

> Got a derbi- stock 30mph

> Added Tomos Tecno Estoril and, 13mm SHA, upjetted-

> 36mph

> Full rebuild- still 36mph (thats good)

> Ported cylinder- 32mph, less torque, but can

> really wind out downhill and on flats.

> 65cc Parmakit- 36mph, same torque as stock, but

> still 36mph

>

> I have played with an assortment of variator

> weights as well

>

> I have jetted correctly, tried different timing

> and so on. I know people who have stock cylinder

> ones that are pretty fast, I have kitted quite a

> few bikes before, using 13mm SHA's and got ~45mph

> out of them, but I am at a loss with this bike. It

> just doesn't want to go faster.

>

> Any ideas?

Take it back to the pros at West Coast Mopeds and tell them not to fuck it up like all the other Mopeds thy can't fix. (edited)

Re: Derbi Piston Port stuck at slow

With my stock ported pp derbi, phbg 19, 6roller and a shitty turbo pipe I was doing upper 40's on flats with great takeoff and torque.

Re: Derbi Piston Port stuck at slow

with my stock ported pp derbi, 19phbg, tjt and a hack and weld gigantor chamber, pietcard cdi, 19x24 gearing... 52mph.

Re: Derbi Piston Port stuck at slow

My PP TT had a quite large rear sprocket, I think it was 36 and with a stock cylinder, pipe and 15 sha it went 36. Then I put a 26 tooth rear sprocket and went a lot faster. Like 10 mph faster.

Re: Derbi Piston Port stuck at slow

the 3 roller varios suck

Re: Derbi Piston Port stuck at slow

ok, so something is up. I am at a loss with this bike being so slow. gearing is 19x30, timing is at full retard, no air leaks and idles perfectly. WHen I get home this afternoon I will check to see if how far from TDC the points are opening and re-gap the plug

Re: Derbi Piston Port stuck at slow

Could the belt be slipping heavily?

Re: Derbi Piston Port stuck at slow

I had my stock derbi pp, hacked stock pipe, ported, stock gearing, light weights and 14mm SHA doing 41 gps...

3 rollers are way more fun without the shitty derbi weights.

Hardware store tech yo. Also, I've almost halved the weight in the vario since this post. Running like 16g total w/ stock contra and clutch springs.

Also... "timing is at full retard" means nothing. Time that shit with a light. Prolly 17* area. North of there is too much for that many revs on stock shit and gears even with all that cooling area. (edited)

Re: Derbi Piston Port stuck at slow

I actually made a set of those weights, with another set of inserts that are even lighter, and made a super light set that is mainly plastic with a small amount of aluminum in the center. None of them really change the top speed. the lightest ones get it to rev out a bit more, but is ultimately only 1 or 2 mph faster than the 'heavy' set I made. I will check the timing when I get home today

Re: Derbi Piston Port stuck at slow

derbis are really sensitive to timing. "full retard" is probably why your bike is running like shit. actually time it with a light. stock timing is 1.8mm BTDC for them.

i've ran derbis with retarded timing down to 1.2mm BTDC and they ran like poop and lost 5-10mph. put it at 1.8mm BTDC and you'll be happy. read the manual, it says 1.8mm BTDC is the proper ignition timing.

Re: Derbi Piston Port stuck at slow

Ill time it when I get home tonight. Thank you guys for the help! If it turns out to be timing ill feel like a noob...

Re: Derbi Piston Port stuck at slow

#CrazyWayne™ rocks. #CrazyWayne /

Wow a n/moped shop that don't time things.

Your a fucking jank it loser.

Re: Derbi Piston Port stuck at slow

Wayne, why are you even here? You mad, bro?

Re: Derbi Piston Port stuck at slow

#CrazyWayne™ rocks. #CrazyWayne /

No your just pathetic your running a moped shop and you can't fix/time shit.

So you come to the forms for a spoon feeding.

Re: Derbi Piston Port stuck at slow

lol yep you got it.

Re: Derbi Piston Port stuck at slow

I dont know if it helps, but just to let everyone know, this is my personal bike, I will not be making any money off of it.

Re: Derbi Piston Port stuck at slow

ok, still having problems, not much difference. Timed to 1.8mm BTDC, B7HS plug gapped to .451mm, points gapped to .407mm. up the slightest hill it still does barely 30. 0-20 has a decent amount of power, but still only pulls like my proma Hobbit. any ideas?

Re: Derbi Piston Port stuck at slow

I blame the 13mm SHA. Smaller then stock?

Is that restrictor still in the intake too?

Also my Promo Hobbit pulled like crazy...

Guessing you need some variator tuning.

Re: Derbi Piston Port stuck at slow

variator tuning is my guess now too

Re: Derbi Piston Port stuck at slow

12mm is stock. Restrictor has been removed. I have tried all different kinds of weights except the stock ones. I'll try them and see how it goes.

Re: Derbi Piston Port stuck at slow

do you have a tjt, derbi 6 roller or the stock 3 roller? if you have the stock 3 roller, lose it. they're trash in my opinion.

Re: Derbi Piston Port stuck at slow

stock 3 roller. I feel if it isnt revving correctly, then a variator is not going to fix the problem though. but who knows, maybe I will try it.

Re: Derbi Piston Port stuck at slow

Suck the stock varios may, but 36 with a kit and pipe is something else... Not the vario. Unless you aren't fully variating with whatever weights you've got in there.

Is it jetted right and what kinda condition is your ignition in?

Re: Derbi Piston Port stuck at slow

try running only 2 stock weights to see if there is improvement..

then get a tjt or 6 roller so the weight is even

Re: Derbi Piston Port stuck at slow

if it isn't revving correctly it could be the contra spring is worn out, or the variator isn't tuned properly. you say your timing is spot on and the plug is gapped correctly. either you're terrible at tuning or you just haven't tuned it enough. i'm guessing you just haven't really dialed it in enough. start with the variator and then let us know.

Re: Derbi Piston Port stuck at slow

I am getting full variation. I did find a small air leak right at the carb clamp. gonna take care of that tomorrow. I also got a few new spark plugs I am going to give a try (doubt it, but you never know). I am also going to try a different carb and see if that does anything. I do have a 28mm OKO laying around...hmm maybe not haha.

Re: Derbi Piston Port stuck at slow

air leak fixed, went on a 3 mile ride at WOT pretty much the whole time and got up to 36 on flats, 42 down a slight hill but it took a while. killed the engine after about 1/2 mile of WOT on flat and pulled the plug and its a nice dry chocolate brown color. WTF this is driving me crazy.

Re: Derbi Piston Port stuck at slow

Got it figured out thanks to Shannon of Mosquito Fleet. The lightest weights I had made were still too heavy for it to rev out correctly. ran 2 of the lightest weights in the 3 roller and it cruised up a big hill at ~25mph, still gotta go lighter!

Re: Derbi Piston Port stuck at slow

..... yes.... we had been saying variator this entire time :)

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