Shaun's (AR's) CRM250AR/CR250 Conversion

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Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 09:39

This will take a while to finish (getting the photos to fit (some http addresses don't yet go to photos)) but Shaun has sent me a write up of his project and I'm posting it up bit by bit -

OK, so here’s a basic story of how I (Shaun) transformed this:

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Into this:

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This is something I have wanted to do for quite a while as all my mates were suggesting it would be so much easier riding something more modern and lighter. However, nothing out there really took my fancy. I love my two strokes, but I hate the thought of pre-mixing. I don’t want to go orange as I don’t want to be like everyone else, and no other two strokes out there are built anything like as robust as the CRM. However let’s be honest, the weight, age and suspension do let it down a little.

I had owned an AR for 3 years prior to starting this project, and loved it to bits. It was suffering from heavy use and wear and tear, and was due a major overhaul. I was originally planning to completely rebuild it, however eventually decided against this, mainly due to the weight and age.
Someone on this forum (and I can’t seem to find the post anywhere) posted a link to this: http://www.uzushio-racing.com/fream.htm (click WCRM250/AR at the top)

After seeing that, I realised that the conversion could be done, and that it looked amazing. I sat imagining an enduro version, but it was just a dream at the time.
Later on, someone else (and again, I can’t find the post anywhere) posted a link to an AR engine on ebay, and it was then I decided I’m going for it!! I made sure the engine was mine, and not long after, somebody ELSE posted a link to our German friend selling a load of Mugen bits for the AR. I decided this was an opportunity not to be missed and bought an ECU, cylinder head, and later jet kit.

The engine sat around for a while, and I started thinking about what on earth I was going to do with it. I didn’t tell too many people my plans as I wasn’t sure I could even pull it off. I also thought it would be a nice surprise for most of my trail riding mates as we had often talked and joked about ‘imagine a CRM engine in an aluminium frame’.
To cut it short, I bought an absolutely mint 2007 CR250 off ebay which had only done a few hours and bought it to the workshop.

Anyway, enough waffle, here’s the interesting bit….
Before:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 09:53

Starting:
The first thing was to rid the CR of it’s engine, exhaust and loom etc, this was all done in a few hours as we were all eager to see if the CRM engine fit. The quick answer was yes and no, it fit in the chassis, which was important, but wouldn’t seat with the existing engine mounts in place, so I quickly grabbed the hacksaw and angle grinder:

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Initial thoughts were that the sprockets were well out of line, and the exhaust would never fit:

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However, this couldn’t be proven until the engine was squared up, needing two off special bushes for the pivot at the swinging arm end. This would square up the engine, then I just had to get the pivot angle right. I think the original CRM steel bushes just fit, but the exhaust port was fouling. This determined the engine had to be shifted left slightly, but not too much as this took the sprockets even further out of line.

After several careful measurements and a fag packet sketches, the spacers were made and the engine was in an squared up. I cleaned up the chassis and completely removed the original engine mounts so there was no trace of their existence. I must emphasise how I didn’t want this to look bodged or really modified.

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This took a considerable amount of time, and now the bike was a rolling chassis with no engine mounts – A perfect start!!

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 12:23

I then lifted the engine in, using the new stainless steel bushes, and a piece of wood to get the height/level roughly right:

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I was really happy with the engine in place, I thought it looked good, but I knew I was still a long way off. It was clear a standard type exhaust wouldn’t fit, and after chopping and playing with the DEP as much as I dared without wrecking it, I decided it needed a flange collar type:

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To get the engine level, I had to try a few things in place, although unfortunately could not test the exhaust angle as the standard one wouldn’t fit. I measured and test-fit lots of bits, but basically ensured the ‘Honda’ writing on the generator cover was level by eye and decided to go for it. The next stage was to make the engine mounts. I began by making cardboard mounts, as it’s much easier to cut and shape to get it right before cutting metal:

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I then got hold of a 10mm thick aluminium plate, and began marking and hacksawing:

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Once I was happy with the bottom mounts, I mounted these in the chassis:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 21:50

I then began to make the top engine mounts, it soon became apparent a lot more material from the original mounts which I thought I could use had to be removed, so it’s back out with the engine and in with the grinder and file:

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Not only did the top mounts have to be made, but 4 off special engine spacers. I decided to give plenty of room in both directions so that if at a later stage the engine had to be moved left or right this could be done easily and the welding would remain permanent. This is the finished engine mounts and spacers ready, I was really pleased with them after I’d polished them. Bear in mind I made the engine mounts with a hacksaw, file and pillar drill, and finished with wet and dry. Plus one had to have some milling done (I cannot claim this):

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The engine was then put back in with the mounts in place to ensure everything fit and looked right:

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I had a fixture made to hold the mounts when welding to avoid any warping, this was basically two tubes which represented the actual engine:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 21:59

Chassis all ready for engine mounts welding:

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First the bottom end was put in place, and all bolted up. The engine mounts were tacked in, engine removed and fixture put in its place to hold the mounts.
At the same time I chopped off the bracket for the chain steady on the swinging arm, and moved it 5mm to accommodate for the sprocket alignment:

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The engine mounts welded in place, this was really exciting:

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I did a lot of research into exhaust, and decided to use the pro-circuit platinum for the CRM250 AR which I ordered for the USA:

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I then began to rebuild the bike with the engine properly bolted in (minus head steadies) and places on the exhaust (roughly):

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 22:06

The exhaust fit, however fouled on the chassis, and the rear bracket wasn’t right:

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I also knew somehow all this lot would have to fit on the bike somewhere…. Eek:

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It did feel like progress was going relatively quick, all the above being done in just a few months, and it seemed I would get the conversion done much quicker than expected…..I was very much mistaken!!

I started to offer things up like the power valve servo motor and such like:

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And I got that excited, I built as much as I could to get a feel for how the bike may look:

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After mounting the rads, it was clear that there wasn’t enough room for the pipe which joins them at the bottom.

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I also found a fairly convenient place for the ECU, well I suppose the only place it could go really, however decided to mount it properly at a later date:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 22:17

I also ‘roughly’ mounted the original AR loom:

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These were later polished to a mirror finish.

I next put the carb and throttle in place, this again was becoming exciting!! The carb seemed to fit quite well, although close between the chassis and rear shock. Also the carb diameter was much smaller than that of the CR rubber from the airbox – I decided to fix this at a later date.

[img]http://i26.photobucket.com/albums/c122/ ... 04.jpg[img]
[img]http://i26.photobucket.com/albums/c122/ ... 05.jpg[img]

I tried the tank on with the carb and loom and other things on to check for fitment. It was becoming tight, and I knew the tank was far too small, being only 7.5 litres I think.

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 22:25

I then messed about with things like the horn, capacitor, solenoids and servo motor to find suitable positions. I also played about routing the loom and throttle cables to avoid entrapment when the tank was on. I decided not to do too much as I knew I was after a bigger tank. I looked; and my two options were Clarke and IMS. I looked at several photos, and sent several emails. It seems the Clarke tank goes much deeper into the chassis and towards the cylinder head. Eyeing up my bike and photos of the Clarke tank, I decided this would not fit, and took the risk of ordering the 12 litre IMS tank from the USA. When this came I was sooooo nervous it wouldn’t fit, but it did…. Kind of!! It made space even more tight, in particular for the cables, potential hose routings and wiring loom.

IMS Tank:

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I also decided now that the engine was properly in place, I could measure the distance the sprockets were out of line and have a spacer made. I did this using a straight edge and replica putty, and measured the gap with a vernier once the putty had gone hard. I think it was around 5mm, but was difficult to measure accurately as there’s quite a bit of play in the sprocket/output shaft:

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After I did made a drawing, I had one of the lads make me a spacer:

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This was later to me made lighter by removing excess material. Unfortunately it was stainless as I couldn’t get hold of ali bar big enough.
I made part of the servo motor bracket and offered it up. I designed it so it could be moved slightly at a later date if necessary to save un-doing and welding.

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I decided the best bet was to chop off the existing radiator mounts and move it up enough so that the bottom joining hose cleared:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 18 Jun 2012, 22:34

Next I labelled up the loom and began fitting things associated:

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In the mean time, I decided to have a slightly longer exhaust collar made to clear the manifold from the chassis. This had to be around 10mm longer than standard, and I
had it machined out of solid stainless. I did the hand fitting myself to shape it correctly:

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Chassis back, engine in, new collar on:

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Power valve serve mounted:

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Rads moved up 10mm, bottom rad clears with special ignition coil bracket I made:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 19 Jun 2012, 07:48

Horn and capacitor mounted:

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Exhaust now clears chassis:

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Bike semi-re-built again to trial fit things:

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Steady progress and things are starting to come together, still an awful lot to do at this stage. This is the point I started worrying how on earth I was going to pipe up the rads, so I started getting odds and ends, and working out what joins and bends I needed:

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I also started to think of ways round mounting the exhaust properly, both the rear silencer, which was to be a DEP nicked off my old AR, and the rear bracket on the Pro-Circuit expansion chamber. The front lower bracket luckily bolted up using the original CRM mount and a spacer I found in the workshop which happened to fit. The bracket for the DEP pipe was clearly out, and the CR silencer/subframe used two small brackets rather than one:

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On the manifold, rather than using extra brackets and to avoid it looking bodged, I decided to neatly chop off the existing bracket and make a brand new one at the correct angle. This was made from stainless, however where the plating was removed I had to paint it as I HATE rust!! I did the work all myself bar the welding (Might as well leave it to the professionals).

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Fits nicely:

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And finally painted:

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 19 Jun 2012, 08:01

I really, really wanted a CRF headlight, too keep the subtle Honda theme, and many aftermarket ones look out of place. It took me ages to source them, and the price was shocking, plus hardly anything available on ebay. Eventually though I did manage to get the plastic and the glass headlight separately on ebay for very good prices, however of course the CR had no mountings for this (later discussed).

In the mean time, between me and Gary at fusion-mx, we designed the custom graphics which I’m still to this day thrilled with and wouldn’t change. I gave him rough designs via email, photos and sketches in paint etc. After many, many tweeks, eventually they were perfect and on order, along with new plastics. I was chuffed when they arrived:

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Obviously the first thing I did was try them on the bike, and oh did this get me excited and put a smile on my face:

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Anyway, as mentioned earlier, now came the mounting of the headlight. This was a fairly tricky one as the original should be rubber mounted, however not too challenging in comparison to other bits of the bike. I had the special top-hat washers made once I’d worked the sizes out, and made the brackets myself:

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The larger bracket was later powder coated, and I polished the stainless triangle brackets.

The next thing on the cards was sorting the wiring loom!! I had already labelled it and worked out where everything went pretty much, but I had to wire in the aftermarket headlight and tail light, kill switch and ignition key, along with all the new switch gear, brake light switches and Trail Tech speedo. I spent a lot on the electrical items as I was searching for quality and reliability. I also chose to used waterproof 2 and 3 pin plugs where necessary, for ease of assemble and obviously so they’re waterproof and therefore reliable and durable.

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A few cups of tea, masking tape and a multimeter had the wiring pretty much sorted.

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Once this was all in place, I managed to test it on my old running AR, and everything seemed to work fine!! However when finally crimped I couldn’t get a spark… which made me extremely annoyed!! I traced it and found that I has mixed the kill switch and ignition wire on the loom up (I remembered the labels had fallen off and I assumed the thicker wire was for the ignition).

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 19 Jun 2012, 08:07

I tried the loom on the bike and routed it many times to avoid entrapment and melting!!

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I then decided to make a fancy sprocket cover with holes for ease of cleaning. This started with cardboard template as usual, then a thin piece of aluminium sheet carefully shaped and drilled, and a couple of black nylon spacers made.

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This was later powder coated when finished and I’m extremely pleased with it!!

Next was to mount the rectifier/regulator and the ECU. Obviosuly these had to be carefully placed to avoid damage, water and to keep the regulator cool. The regulator was placed in a similar position to the standard CRM, however later found to foul the shock, so I had to file minor amounts off the cooling fins. The ECU was located in the airbox which seemed obvious, but the exact position was difficult to determine, as the wiring was tight, and I wanted it soft mounted and easy to remove. My initial thought was to make a mock ECU and vacuum form a holder to fit under the seat, but decided this wasn’t the best option. I experimented for a while with cardboard, and finally came up with a design using some thick foam and ali sheet.

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 19 Jun 2012, 08:18

I was fairly happy with this although it wasn’t quite finished. I then decided to sort the exhaust completely. I started by a cardboard bracket for the additional subframe bracket:

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And then making it out of ali:

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I then carefully chopped off the original DEP silencer bracket:

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And cleaned up the silencer as best I could:

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The new bracket I made was then welded on:

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I cut down and shaped the original DEP bracket to suit:

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And then this was welded on and the exhaust was sorted!! Getting the angles correct was quite critical.

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It was also time to properly pipe up the rads… which I was slightly worried about due to lack of space. This took ages and lots of trial and error techniques, including purchasing lots of connectors and various size and shaped silicone hosing. I also had some special T-Pieces and reducers made at work as the exact sizes weren’t available.

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My next massive dilemma was the autolube tank. I did not what so ever want to have to pre-mix, this was one of the major things for me keeping a 2 stroke and therefore doing this entire project. I was now so close to the end, and was worried about how I’d overcome this task, and didn’t want to bodge or avoid having autolube. To cut a long story, I tried all sorts of little bottles. For weeks I was emailing companies on fleabay asking them to kindly measure small tanks they had advertised for scooters (ie rad headers and small 2t bottles). I also tried nitro car and plane fuel bottles. In the end I decided to just make one out of ali.

I experimented with shapes and sizes… bearing in mind there was very little space left, the angle had to be correct, capacity sufficient and ease of filling. In the end I managed to fit a section of pipe insulation in… and began calculating how much 2t a tube of this size could hold.

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I then ordered a piece of ali tube to the maximum allowable diameter and cut to length off ebay, and made two end caps using aluminium sheet.

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In the mean time also I was playing with mounting the two fuel solenoids and had to move the chain runner to accommodate for the sprocket offset.

[img]http://i26.photobucket.com/albums/c122/ ... 57.jpg[img]

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 20 Jun 2012, 09:08

I decided to lower the bike, as I’m not the tallest bloke in the world!! In fact far from, and it makes handling and dabbing the floor a dam sight easier.
Koubalink, lowers the ride height by about 1 ¾”:

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I also ordered a CR bashplate off ebay (actually a gift from me ex girlfriend):

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This had to be modified slightly to suit the CRM engine casings – Just a little heat and bending was required. Some bits in the mean time, including my engine casing and previously made pieces turned up from the powder coaters also:

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Also I polished the two headlight mounting brackets:

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The previously made bottom bracket was now powder coated and I popped in the rubber grommets:

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I made some drawings for the inlet and outlets of the mini 2 stroke tank, based upon measuring the original CRM ones so I could use the original cap, filter and piping. I then chopped the tube/tank and angled the outlet:

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This was then tack welded in place. The following photos show the progress of the 2 stroke tank. It was very difficult to ensure it cleared and vibrating or hot parts, and I made two special rubber mounting brackets. To get it welded correctly, I had to use masking tape and markings, have it tack welded, then check it fit, seam welded and then tack weld the next piece and so on until it was complete….

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Re: Shaun's (AR's) CRM250AR/CR250 Conversion

Post by knackeredMk1 » 20 Jun 2012, 09:19

Finally it was finished, the side bracket was used to mount one of the solenoids:

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And finally it was powder coated… the lads at the powder coaters wondered what on earth it was. I must admit, It does look amazing!! ;)

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The total capacity is 350ml…. which should do 150 miles…. More than a normal days trail riding, however I now carry spare as I did get caught short once!! I also tidied up the loom once I knew it was all working, and taped it a bit like a tree:

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Everything was pretty much done, and to be honest I was buzzing…. Next came the best bit… the strip down, clean, engine rebuild and final build… knowing everything should go back in place. I was still extremely apprehensive though. I began cleaning the filthy engine:

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And polished the modified DEP silencer, from:

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to:

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As mentioned earlier, the standard AR carb diameter was too small for the CR airbox rubber, so I made the necessary measurements, made a drawing and had a special sleeve made at work. I filed down the original lip, and bonded the new sleeve on using araldite.

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The carb also had a thorough clean using a sonic bath, carb cleaner, Cillit Bang and an airline!!

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And jetted it using the Mugen jet kit (thanks for your help Glenn), with a best guess at the jetting, using the advice on this Forum under ‘Modifications’:

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Somebody at work very kindly polished the head steadies I made on a machine, talk about SHINY:

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