Meddling with a Wisp

Hi guys and gals from across the pond,

Firstly I'm a complete two stroke novice, so I apologise if I ask daft questions. I set out to buy a wisp as a quarantine project (ended up with 3), to make things worse I've bought the 66cc Airsal kit hoping it will get round the wisp gearing issues. My question is, can I fit an AV89 head, are the cast mounts roughly in the same place as the ones on the earlier tear drop head? Would it fit between the frame mount or need machining to width? Is this a really bad idea?

Thanks in advance,

Tom

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Re: Meddling with a Wisp

Did you pull that one out of a forest, or is it green spray paint?

Re: Meddling with a Wisp

Jeremy Homser /

The mounting location on the cast mount heads are not going to line up without some work. You might be able to reuse the old mount bracket on a newer head

Re: Meddling with a Wisp

> Jay Rivett Wrote:

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

> Did you pull that one out of a forest, or is it green spray paint?

Yeah, it got pulled out of an evergreen hedge, seized solid but the seller wanted me to have it as it has a complete carb and a stand. I can't get near it without getting covered in sap!

Re: Meddling with a Wisp

Cheers Jeremy,

The plan is to fit a stuffed crank, kit and maybe the av89 head. I'm not planning on this being a high speed bike, I haven't got that much of a death wish, just better acceleration.

Also the meddling isn't just restricted to the engine!

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Re: Meddling with a Wisp

> Tom Boyd Wrote:

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

> can't get near it without getting covered in sap!

Sounds like it's time for a hot pressure wash . ;)

Re: Meddling with a Wisp

> Tom Boyd Wrote:

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

> Cheers Jeremy,

>

> The plan is to fit a stuffed crank, kit and maybe the av89 head. I'm not

> planning on this being a high speed bike, I haven't got that much of a

> death wish, just better acceleration.

>

> Also the meddling isn't just restricted to the engine!

Now this is going to be cool... :)

Re: Meddling with a Wisp

Cheers Stephen, this idea has been rolling round my head since I was a kid. The seat is off my old tomahawk and still has blobs of yellow paint from when I repainted it when I was 10 but it's being taken away on Friday to get retrimmed by a mate who works at Lotus cars. I've given him full artistic license apart from it's got to be a bit bat shit crazy, so can't wait to see what comes up with. I think it going to work, I'm 6'2" and dwarfed the std wisp, stick a chopper seat on and its comfortable as ...., I was going to keep the engine standard but what the hell do you learn from that.

Hi P D, I think the diesel vat is calling for the green one!

Re: Meddling with a Wisp

Seriously, this was never going to work was it 🤣

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Re: Meddling with a Wisp

Ha . Diesel will likely cut the um , 'natural beauty' . ;)

Re: Meddling with a Wisp

Ayup,

Most of the bits have arrived for the engine build, enough to start tearing it down. Starting to mark out for case matching but the Airsal cylinder has an enclosed window in the skirt, has anyone removed this? I'm looking at it thinking how much turbulence it will cause and wondering if it will significantly weaken the skirt if its removed, same goes for he piston. I'm sure someone has tried this but cant find anything by searching.

Any advise guys?

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Re: Meddling with a Wisp

This is cool.

Re: Meddling with a Wisp

Finished cutting the new squish band, couple of dremel marks and casting flashes still there but I'm more comfortable hitting things with hammers so I'm happy at my first ever go at this.

Now going to start looking at the case match, any thoughts on skirt mods? There is little love for mopeds in the uk, especially tuning them, but you guys are properly on it!

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Re: Meddling with a Wisp

Most excellent project.

Those lead in windows for the transfers need to be a bit better matched up, if you decide to take off the bridge across the bottom of the cylinder skirt you would want the round the corners of the cutout so you dont have pointy ends which might want to curl towards the piston skirt as the top part of the cylinder becomes heat soaked.

I would also suggest to not hog out the top of the carter halfs too much, just profile the tops to match the cylinders lead in to the transfers. Also touch the top of the oil journal for the mains with a larger drill bit so it gains a funnel sort of shape, that will help to collect and direct some parasitic oil towards the mains.

Read about someone throwing on a 13t front sprocket/pulley assembly to give the power somewhere to go (as in faster).

Not a negative comment, just an observation: Could have shaved the stock low cr hemi-head and cut a short squish band into it, the closed chamber heads have way too much shrouding at the spark plug.

Certainly going to follow this build, very interesting indeed.

Re: Meddling with a Wisp

Hi Rebel moby, thanks for your advice, I've learnt a huge amount by reading through your posts about moby tuning.

Very good point re plug shrouding, I'll open it out a bit, there's plenty of material there to work with.

I bought the barrel amidst late night whisky fueled enthusiasm, when it arrived I found I'd ordered the wrong shaped one. There is nothing like treats here so I'm ordering bits from france, returning it was too much of a ball ache. I then started researching what an av89 engine was and found the hc head, buying a new decomp was going to be £16 but the hc head (inc decomp) from france was £24.

Not sure about gearing for speed just yet, wisps are renowned for their terrible handling, I measured the trail at a 8mm!

I am very wary of removing too much material from the cases, not rushing it, I'll definitely do your oil feed mod. Any and all advise greatfully received.

Re: Meddling with a Wisp

Ayup,

This is probably a very conservative case match. I see your point Rebel on not hogging out the case too much, I found that the walls around the ports are only 2mm thick so I just worked on the top 6mm (the thicker base bit), and opened up the oil way. Anyway, enough roughing out for tonite, finish them with files and paper tomorrow

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Re: Meddling with a Wisp

Worse than terrible handling would be not being able to stop with those Sturmey Archer front brakes, at least the rear wheel has a proper moped type hub. You may want to add some cross cutting to the brake shoes to improve their braking capacity, even if you just have the kitted engine and do not up the gearing.

You had better make sure the tyres are in top shape.

Do you know of Brian Alpin's "Alpin of Bristol" shop yet... he would be an excellent resource for NOS bits as well as vast expertise in everything Raleigh.

> Tom Boyd Wrote:

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

> Hi Rebel moby, thanks for your advice, I've learnt a huge amount by

> reading through your posts about moby tuning.

>

> Very good point re plug shrouding, I'll open it out a bit, there's

> plenty of material there to work with.

>

> I bought the barrel amidst late night whisky fueled enthusiasm, when it

> arrived I found I'd ordered the wrong shaped one. There is nothing like

> treats here so I'm ordering bits from france, returning it was too much

> of a ball ache. I then started researching what an av89 engine was and

> found the hc head, buying a new decomp was going to be £16 but the hc

> head (inc decomp) from france was £24.

>

> Not sure about gearing for speed just yet, wisps are renowned for their

> terrible handling, I measured the trail at a 8mm!

>

> I am very wary of removing too much material from the cases, not rushing

> it, I'll definitely do your oil feed mod. Any and all advise greatfully

> received.

Re: Meddling with a Wisp

For unshrouding the spark plug I wrote an article for this before, just as a preamble, the idea of unshrouding the spark plug is so it is not hiding in a well. With easier access for the spark to be exposed to the fresh air-fuel mixture it will ignite a more robust flame kernel. The pathway from the ceiling of the transfers to the plug center is also partially obstructed by the "bumps" that raised the compression ratio. A slight shave to these bumps will clear that passageway. You will need to tinker about with your squish band after unshrouding because you would want to restore the compression ratio. The 5cc volume works well with the stock bore, you will need to make adjustments for the overbore.

ARTICLE

Stock AV7-AV10 heads have two basic shapes: open chamber, which is hemispherical; and closed chamber which has a large protrusion on each side of the spark plugs.

The volume of these heads is approximately 5cc for the closed chamber and approximately 8cc for the open chamber.

Stock 5cc heads are slightly restrictive towards the flow of incoming charge from the transfers.

An easy fix is to remove some of the material shrouding the access to the spark plug.

Then restore the original volume of 5cc by shaving the head.

You would need a marker, some files, some alumimium oxide papers (220, 600 and 800 works well), kerosene and fine steel wool to finish to a good polished look.

Basically you need to shave down a strip from the bumps on either side of the combustion chamber.

The strip needs to be 3mm at the center of the strip and taper at both ends.

Then remove the extra material around the spark plug thread insert at the top of the chamber.

Using hand files and aluminium oxide papers this is a 20 minute job.

Use a permanent marker to draw on the head where you will be removing the material.

The material removed will be to leave a 45 degree ramp, which you would them blend into the surrounding material

so the roof of the combustion chamber is smooth.

Check that there is no lip at the front of the chamber, this lip should also be blended in so there is no pocket when the piston is at TDC.

Start with reworking the sides of the chamber.

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After the sides are roughed out then move to the periphery of the spark plug insert.

Reworking this area calls for blending out the ridge between the chamber and the insert.

Carefully pare it down for a smooth transition.

After roughing out the material smooth out the transitions with 220 paper, then 600 and finally 800.

Use the paper wetted with kerosene. Finally buff out the work with fine steel wool soaked in kerosene and wipe out with a rag so she shines.

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Next shave the head to restore the volume of material removed.

Use a syringe with some 2 stroke oil to measure the volume of the chamber.

Stock is approximately 5cc with the right sparkplug installed (Champion L86C or NGK B6HS or equivalent).

Note how much extra volume there is in the upper chamber.

If you are attempting to go for higher then stock compression ratio calculate the target volume you need before you start to mill.

Re: Meddling with a Wisp

Damn Reb, that is a perfect explanation for hicomp head mods!! Thanks for taking the time to write that post (and repost it here), I hadn't come across it but I didn't expect to be using the hc head so hadn't searched for it, I still have a lot to learn.

Supposedly the only thing in the wisps favour is decent brakes, smaller diameter greater affect and all. Good shout on hatching the front pads tho.

Tyres are new, went white walls even though I'm not a fan really but somehow they seemed right for the project.

I've heard of Alpins, the name crops up time to time but haven't found any contact info. There are a few people around here that have good stocks of moby parts. Weirdly I ordered a coil of ebay which arrived first thing the following morning, the chap I ordered it from lives in the next village over so he hand delivered it, tis a small world! He's selling cashews at the moment and I'm getting tempted, there isn't a decent exhaust amongst the wisps.

The crankcase at end of play today.

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Re: Meddling with a Wisp

Read up on here about modding the crankcases to fit and remove the crank seals from the outside. I decided to set them up on the mill and bore them out.

First dog the cases down and clock them in.

20mm ripper to take the majority of the metal out.

Set up the boring head and bore it out to 20.8mm (measured with a mic and bore slips), leaving a .1 lip to help hold the seal in place but still allow easy figment.

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Re: Meddling with a Wisp

The other half was set up on three ground pads because of the register lip on the inside.

The finished case with a rad on the outside.

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Re: Meddling with a Wisp

I've never seen those angled block thingamajigs with the micrometer, what do you call them? I'm guessing there's some kinda calculation involved to find the inside diameter?

Re: Meddling with a Wisp

> discontinuuity _ Wrote:

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

> I've never seen those angled block thingamajigs with the micrometer,

> what do you call them? I'm guessing there's some kinda calculation

> involved to find the inside diameter?

I inherited telescoping gauges from my dad’s days of aircraft maintenance. I guess the blocks are a simpler way to accomplish the same goal. Maybe not ideal for some situations. I take mine for granted, since they’ve always been in my life. Never have to do it another way.

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Re: Meddling with a Wisp

Hi discontinuuity,

I only know them as bore slips, might have another name. They are a piece of piss to use, they are precision ground with an angle on the inside and a rad on the outside, put a pair (of the right range) in the hole, slide them until they're tight in the bore and mic across. Papa called it, they are old tech and superseded by bore gauges, a lot of my kit is old tech. They are handy when you have a worn bore and need a quick read of the minor diameter to get a starting point for a rebore.

Re: Meddling with a Wisp

Huh, interesting. I see the radius now that you mention it.

Looks like something you'd need 3 hands to work properly, like thread wires

Re: Meddling with a Wisp

Nah, once they're tight they're tight and wont move about. They didn't slip with the weight of the mic left on them when I took the pic, and that's gripping against bugger all material.

Re: Meddling with a Wisp

Mannaged to get the whopper project pushed on. Had to bore the cases to fit the new crank, case measured 70.2 / 70.4, crank is 70.5, case machined to 71.

Clocking in the bearing land.

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First cut clearly shows case halves are out of round.

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Now to get them clean ready to start putting it together.

Re: Meddling with a Wisp

Unlikely that you would need to change the spi seals often but still a good mod to the engine casings. I would suggest to get the 15mm crank seals which are rubber backed, rather the steel exposed case type. The rubber ones are more forgiving to install and will provide a good seal at the seal to bore union.

I have tapered gauges and a cone set in my toolbox in the shop, "accurate enough" for the type of precision we need on our bikes for general machining.

Aplins has been in business over 5 decades from he same shop, and they have yet to need a website or other interweb foolery. You can give BriaBrian Aplin a ring on 0117 977 7376 or visit his shop at 395–7 Bath Road, Bristol. Open during regular business hours but I believe he is closed on wednesdays.

Re: Meddling with a Wisp

Ayup,

Got the cases back from being vapour blasted, bit pissed as they accidentally lacquered them, supposedly high temp but I doubt it, I'd rather they were raw and just rub em down with acf50.

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Set the crank up on some old parallels, warmed and fitted the bearing.

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Warmed the case and crank fits perfectly, even clearance all the way round checked with feelers.

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Re: Meddling with a Wisp

Fitted the piston and barrel to find the transfer port was covered by the piston crown ( then read up on here to find this is a common problem)

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So cut a 1.5mm base packer and shaped it to the same size as the bottom fin so I gain extra an cooling fin

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Transfer port is now clear but there's a bit of a step up to the exhaust port.

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Is this a serious problem guys? Being new to this I dont want the dive in and end up chipping the nikasil. I'm looking for more torque not massive hp or high rev.

Hey Reb, thanks for all the info! I'd read in one of your other posts about the seals, and have followed your advice and fitted them. They fitted a treat too, the steel caged ones were a bitch to get out so I'm more then happy to ditch them.

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