Derbi flat reed, slow take off

I have a Derbi DS 50 with a 70 Metra Kit,16:16 Dellorto sha with 70 jet,new 1977 flat reed belt,stock clutch with like new pads,Polini 3 gram rollers(16x13x6),yellow Polini clutch springs. Take off is very slow. It doesn't have the so called Derbi lurch that everyone talks about. Any suggestions on how to fix it? Oh,and it has the original spring in the rear pulley. Thanks

Re: Derbi flat reed, slow take off

If you want to come down to htown, I could maybe.. help you out with a rear contra pulley spring. 70 jet sound low to me.

Q:

How many miles on bottom end .. and have you installed new crankshaft seals? (edited)

Re: Derbi flat reed, slow take off

Joe Fraley /

Just rebuilt the engine last fall. Installed all new crank bearings and seals.Checked the piston to head clearance,if I remember correctly,.77mm which is just about right. As for the jet, I think that it is a little too low.Once you get it moving,the thing will fly

Re: Derbi flat reed, slow take off

Joe Fraley /

I forgot to mention that it has a 75cc Zen pipe that I modified at the header for ground clearance.

Re: Derbi flat reed, slow take off

Ϫ‡☄ಬ∞ ƀƖḬƝƊ ƤǂƿƎ ∞ಬ☄‡Ϫ - Hoke from Black Pipes Moped Gang /

sounds like you need tighter clutch springs

Re: Derbi flat reed, slow take off

Points? Cdi? Whats your timing at? I do right at 1.85mm btdc for kitted derbis (stock is 2mm)..

Still using starter clutch shoes? If yes remove them and see what kind of difference it makes.

70 jet is very small for that kit. Id say you should be in the mid 80s.

Re: Derbi flat reed, slow take off

Joe Fraley /

DS 50's come stock with motoplat cdi ignition. That is what I am using. Timing is set at 1.8mm BTDC.

Re: Derbi flat reed, slow take off

Joe Fraley /

I am still using the starter clutch shoes. I never knew that you could remove them. What does that do?Also, just ordered a set of 80's jets for the carb from Treats.

Re: Derbi flat reed, slow take off

Tighter clutch springs.

Re: Derbi flat reed, slow take off

Joe Fraley /

I have a set of Polini blue springs left to try.I have tried the green and the yellow ones. I have also heard of shimming the rear spring.

Re: Derbi flat reed, slow take off

Iam running a ds50 with a 18mm phbg, 70 metra and head, with the gianelli hiboy, no complaints on the low-end. I havent played with the weights or clutch springs yet.maybe that sha is the problem.

Re: Derbi flat reed, slow take off

at least 100 miles with malossi red mhr springs now, 2 rallies, loving every zoom off the line. the fun went way way up when i ditched starter shoes. well worth it

Re: Derbi flat reed, slow take off

If you want a contra spring, I have some custom made ones. No shimming, .. or you taking about my shim spacer I made for the public?

Re: Derbi flat reed, slow take off

Joe Fraley /

I have some new jets coming from Treats. I think the contra spring may be too weak. The rear pulley seems to open up way too early. I will see if removing the starter shoes helps any.

Re: Derbi flat reed, slow take off

I could of help you with some jets.. and the contra is surely weak after all these years.

Re: Derbi flat reed, slow take off

Joe Fraley /

Removing the starter cluch shoes did help some,but not as much as I had hoped. I'll wait until my jets come and go from there.

Re: Derbi flat reed, slow take off

Joe Fraley /

Got my jets from Treats. Installed the 84 first,way too large. Went to the 80,still just a tick too rich but ok. Take off is a little better but man what a difference in the top end!!! Maybe I will tweek the weights again and try the blue Polini clutch springs.

Re: Derbi flat reed, slow take off

those polini clutch springs are difficult to put on because they don't have the proper "hook" on them to grab the mount points on the shoes... they are doable but you will be fighting with them like crazzzzzy... I have polini springs on my flat reed, i'm forgetting what color but they are decent.

Re: Derbi flat reed, slow take off

your jet size sounds around where i'd think it should be. i have a 76 in my 15phbg. i'm around 24g for the weights myself. also stock cylinder

Re: Derbi flat reed, slow take off

Joe Fraley /

I found an easy way to put on those clutch springs. If you take a small finishing nail and put it on the un attached end, you can put the pointed end where the pivot pin is and use the nail to pry the spring into the hole. Pull the nail out and tap the spring the rest of the way into the hole. Try it, it works real well!!!

Re: Derbi flat reed, slow take off

joe, so did ya install the new contra spring yet? bet it rips out of hole now.

Re: Derbi flat reed, slow take off

Joe Fraley /

Still not where it should be.Hills are a killer. Might have to go to a bigger sprocket in the rear.(stock 17x34) Tires are 100/90/10 Pirelli sc 26(the widest I could fit inside the swing arm)

Re: Derbi flat reed, slow take off

go smaller up front

Re: Derbi flat reed, slow take off

Joe Fraley /

Like how small?

Re: Derbi flat reed, slow take off

sounds like you're having some problems. 14? 12? I dunno. you should be good with 17x34

Re: Derbi flat reed, slow take off

i'll trade ya a 13 or 14 for that 17!

Re: Derbi flat reed, slow take off

Joe Fraley /

This thing is a rocket when it hits the pipe at about 40 mph. The problem seems to be getting it into the power band. I have one more set of stronger clutch springs to try. I am using 3 gram weights currently. Also I am not a small guy so that is also a variable.

Re: Derbi flat reed, slow take off

Joe Fraley /

Changed the clutch springs to the blue polini ones and went to the 2.5 gram weights. This thing will fly once you get it moving!!! I am begining to think that the bigger tire size may be the problem. It may be just a matter of changing one of the sprockets but it is definately better with the stronger clutch springs.

Re: Derbi flat reed, slow take off

we've got a ds50 at the shop that is bone stock apart from the huge fasmem pipe on it (it's meant for 70cc+) and it touches 50mph on the flats... and it gets into the pipe real quick too...

Re: Derbi flat reed, slow take off

† CH∆D † /

What's this about shimming the contra spring? I just nabbed both available at treats.

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