Jump to content

Sped fight 3 de restriction


DougW
 Share

Recommended Posts

From web I can see that the speed fight 3 has washers on the variator stopping it from operating fully and exhaust restrictions.

got it now, stops dead at 8000 rpm no load.

first exhaust restriction is a t piece on the header that adds volume to pipe, like an atac valve on all time , I think, so have pipe off to remove copious rust and this could be blanked off.

just after this is a second smaller t piece tube, connected to a one way valve that will only let air into the cylinder.

what effect might this have ? It’s got a rust hole in it so got to either repair or blank off.

I have seen that having a bleed pipe on the belly of a chamber can boost midrange at expense of top end. I’m guessing a bleed in the header would reduce the negative pulse created by an exhaust?

Also, anyone any experience of Naraku 70 cc kits for Peugeot.?

dirt cheap, for a reason maybe ?

Cylinder exhaust  studs have rotted away and seized in barrel, dremmeled the remains of the nuts off, currently soaking in some acid prior to heat  and penetrating oil, tempted just to get a £50  Naraku kit.

Link to comment
Share on other sites

I derestricted my lads speedfight 2, I cut off the extra pipe on the exhaust and brazed a flattened part of it over the hole with the washers removed from the variator it worked a treat.

On that model there wasn't the extra pipe after this.

I've no experience of the Naraku kit but if those studs wont come out in half an hour I'd probably speed the 50 quid just to avoid the grief!

  • Like 1
Link to comment
Share on other sites

19 hours ago, bowman said:

I derestricted my lads speedfight 2, I cut off the extra pipe on the exhaust and brazed a flattened part of it over the hole with the washers removed from the variator it worked a treat.

On that model there wasn't the extra pipe after this.

I've no experience of the Naraku kit but if those studs wont come out in half an hour I'd probably speed the 50 quid just to avoid the grief!

Well studs done and it is back together. Cleaned exhaust port, put a bit of a bull nose radius on the entry to the transfers on the cylinder base, and removed the air bleed and welded it up.

fair bit of baked on carbon on piston, no bore wear apparent, my micrometers start at 50 mm so couldn’t measure piston.

Left the restriction t pipe on as suspect it might need jetting up a bit after that, job for another time. 

Made a port map for practice and to work out port timings.

Be a sod to port tiny barrel, probably better to raise whole barrel and machine top of to match.

Anyway pre fettle it stopped dead at 8000 no load, now revs to 9000.

Enough mopeds for now off to put a new front tube in KTM ready for Peak District on Saturday 

Link to comment
Share on other sites

  • 2 months later...

Fitted a technigas silent pro exhaust to the speedfight, worked well enough for now , 35 on flat.

More in preparation for the 70 cc kit when he’s is 17 in a few weeks, we got a 17.5 mm carb to replace the standard 12 mm carb.

It came with a 95 main jet, and was way too rich , not revving past 6000 rpm

Standard carb has a 54 main jet, ran very lean with this in the 17.5 mm carb.

Both carbs use 6 mm dellorto type jets, I only currently have a range of Mikuni type jets.

But I do have a 0.75mm jet drill, and this is where it went wrong...

Original 54 jet drilled to 0.75mm, still to rich in the 17.5 mm carb and will not rev.

Original carb with drilled jet won’t rev past 6000 now either...

Selection of jets ordered, then tried original carb , drilled jet, with air box lid removed, foam element held in place with cable ties

Now runs OK , noisey and a little slower than with standard carb airbox, but usable.

So air box lid and snorkel must be very restrictive.

It has a long thin internal snorkel and a very small tubular inlet connected to a long rubber hose that ends under the seat.

The easy route would be to make some holes in the bottom of the lid, but would it be better to “port” the existing set up, increasing the diameter of the inlet a couple of mm and shortening the snorkel ? Out and out performance is not the aim here, just something a little livelier but still reasonably quiet and civilised.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...