Richard's DOHC Cafe Racer...

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Prof
Founder, Choppers Australia
Posts: 5749
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
Contact:

Richard's DOHC Cafe Racer...

Post by Prof » Thu Aug 30, 2018 8:33 pm

Was going to get up pics on progress of Rob's ironhead chopper, but our you beaut computer system is mucking up again and I cannot access my photo files.

However, this machine came in last week and I've made a start on it. Pics still in camera, so accessable.

Richard has spent quite a bit on it so far with a completely rebuilt motor, tidy wiring system and a nice alloy tank and an alloy seat of the internet. Richard has limited equipment and after seeing how well Lar's BM cafe came up, decided to get his finished at The Chopper Shed.

He wants tank mounts redone as it is very wobbley.
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Seat is difficult to remove and he wants a better set up. The seat padding might be ok for a 300 pound gorrilla with iron underpants, but too thin and too hard for Richard, so that needs redoing plus upholstery. Other issues are an excessively loud exhaust and tailight and number plate mountings he wants redone.
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Tank...

I discover the hard way when emptying the fuel from the tank that the filler cap does not seal (at all!!) due to a dip where the welding has buckled the filler neck. Too deep a dip to be sorted with rubber so will have to fill it with some liquid metal and file it back.

Rear mount is only secured with one bolt and moves side to side. Nut is also difficult to access requiring two spanners dexterously delivered with a bit of a twist...
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Front mounts are designed to fit the stock Honda rubber bushes, but are too large a diameter. So some thin rubber strips are cut...
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... and glued into the fronts of the mounts... then trimmed with a die grinder for an easy slide in fit...
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I use Selleys' Shoefix rather than plain Quip Grip. They used to have Shoe Glue, which I think held better... used to swear by it!
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Insecure rear mount. Bolt poked though the bottom of the bracket and could not be kept tightened, so after overcoming considerable resistance (bit like a pollie stepping down from his lucrative portfolio!) I extracted the bolt...
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... and replaced it with an M8 (Nutsert) thread...
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50mm stainless bracket made up and bolted in...
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Setting up for square...
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Hole for second fixing bolt measured up...
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Then another M8 Nutsert, but this time on the stainless bracket...
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Tank bottom needs to line up with seat bottom...
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Tank will be mounted on 6mm rubber at the back. Here the tank packed up the the right height and measuring up to know where to bend the bracket..
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Final bend done in the vice using a small sledge and piece of 75mm 12mm flat bar I also use when bending up battery boxes...
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That works out about right but bracket pokes too far backwards so now a slight forwards bend in this cool little vice bender...
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Now final bend needs a steeper angle past 90 degrees. An easy way to do this is to lay a piece of 6mm steel rod on the top of the vice and continue the bend...
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A bit of shaping and she fits really nicely. Mounting hole marked after double checking that rear of tank is centred...
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I am not a fan of needing two hands to tighten/loosen bolts so I make up a piece of threaded 8mm bar to bolt under this slot. I will use 10mm bolts so this slot has to be enlarged for the tank mounting bolt (yellow arrow) and the hole at the forward end enlarged slightly also for the bolt that holds the threaded plate in place...
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Here it is mounted...
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Rubber gets an indent for button head with die grinder...
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A rubber washer on top held in place by a stainless mudguard washer. Spring washers are of little use on rubber mountings, but star washers usually work, which we use here...
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That's the tank done. It is now nice and firm. Front seat mount also finished tonight, but more on this when the seat is fully mounted... tomorrwo night all being well.
Chopit'nrideit... Prof

Prof
Founder, Choppers Australia
Posts: 5749
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
Contact:

Re: Richard's DOHC Cafe Racer...

Post by Prof » Tue Sep 18, 2018 10:49 pm

Seat...

Now onto remounting the seat. Originally mounted with 4 M6 bolts and nuts the seat was a pain to remove and install. Bolts protruding through bottom of seat had come llose. It was hard to line up and the two front nuts were really hard to access. None of this is good when access to battery and electrics including fuses requires seat removal... really fun if you have a blown fuse on a dark rainy night when your mates just want to get home!!!
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No chance of making the existing set up work, so unfortunately, we'll have to start again. Seat bolts are cut off, the rear two flush and the front two leaving half an inch of thread still protruding because we can use them. Two existing holes (yellow arrows) will be used to secure a high spacer/mount attached to the frame. Ridge in centre is in the way so...
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We make a couple of cuts in the centre of out mount...
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... tap it in, curve the sides and weld...
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We are going to have slots in the mount to receive two buttons mounted on the bottom of the seat at those two protruding threads. Buttons are turned up out of mild steel on the lathe. When mounted on a washer against the seat bottom, there will be a space of 4mm...
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... because the mount which is made of 1.6mm wall rectangular tube will have a second piece of 1.6 welded in to reinforce it. Yellow arrows show a couple of plug welds. Purple arrow shows the double thickness with the edges welded. Cut out allows the buttons to slide in and retain the front of the seat. Blue arrow shows a nut welded (one each end) to retain the mount to the frame
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Hear is the mount installed. Holes in frame are large diameter so a 'mudguard washer' is used under the M6 socket head cap screw. the seat slides forwards over this mount and the buttons locate in the cutouts. Works a treat...
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Now for the rear support. Height of seat at rear has to be measured by sitting the old mounts back in place.. Piece of paper shows the proposed support which will be welded to the frame. It will support the seat and prevent any sideways movement as well...
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Support is made from 3mm x 30mm flat bar. When bending you have to allow for thickness of metal as it bends otherwise you will end up with a bracket that is 6mm too wide...
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Rear support is set as far back as possible meaning a bit of measuring again...
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Welded in place... It is 6mm narrower than the seat because that is the maximum width of the frame at this point, which will also allow some thin rubber spacers which will reduce rattle...
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Rubbers cut and ready to be glued in place...
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So how to hold it all down. Well the simpler the set up the better and in this case one bolt only will do the job. A hole is drilled in the centre of the frame cross member (purple arrow)...
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Thickness of frame at this point is measured...
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... plus the height of the bottom of the seat above the frame cross member...
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What to use for a hold down bolt? Aha! I got a mate to collect a pile of these one time when he went to U Pullit; a spare tyre hold down bolt...
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Tube is welded to a washer...
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... which is then tacked over the hole at the cross member. This allows the bolt to be pushed up from under the frame and be guided right to a corresponding nut on the seat base...
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Seat is now installed and a drill guided through the tube and a hole drilled in the bottom of the seat...
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I collect any thing that might be used in jobs like this and save time machining. This shouldered nut, a threaded tube (don't know what it is really called) has the hex cut off...
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and a mudguard washer welded in its place...
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... which is then pop riveted to the upper side of the seat base. The length is needed because a thick nylon base has been glued to the bottom of the base and this lengthened 'nut' passes through the nylon for a perfect idiot proof line up of retaining bolt and thread...
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Bolt here installed. So now the seat is attached with one bolt that can be tuned without a spanner... quick, foolproof and easy. I always try to use either captive nut or captive bolt to facilitate quick release and tightening. While it takes longer to set up there are two major benefits; 1.to the owner whenever he needs to take something off and 2. to the builder who may have to remove and attach an item a dozen times before the job is finished. In this whole job the seat will be removed at least 25 times. That will more than save the owner money...
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The owner has asked that the seat have new foam upholstering. Because he wants the aluminium of the side of the seat to be seen, we have to make a second seat base that mounts onto this one. The foam will be glued to this and the vinyl folded underneath and glued. This will then attach to the main seat base. First job is to get all the old contact cement off so the second base can sit flush. Toluene dissolves contact cement in a jiffy...
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Clean seat base...
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Secondary base measured up on some 3mm aluminium. Three mil because it is stiff and to allow an edge to glue a fine top layer of foam to...
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Cardboard pattern made of seat hump. Then reduced in size by 4mm to allow for thickness of vinyl and thin foam...
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Because the secondary base will be separated from the main base by the glued vinyl, we trim off another 3mm across the top...
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Marked on the ally and the curve cut with the jig saw...
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Straight lines done with angle grinder. Running the moving blade against a was block with allow the blade to cut the aluminium like butter...
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A hole is cut over where the mounting nut is secured using a hole saw. Lubricate with kero...
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Secondary base in place...
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Two M6 bolts front and rear will hold the two bases together. Here the captive nuts are made from 10mm x 5mm bar. Centre hole is threaded to M6. Outer holes are 3.5mm for the pop rivets that will hold them in place...
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Centre holes are drilled in the base, a bolt tightens them up so the pop rivet holes can be accurately drilled...
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Bottom of the base needs to be perfectly flat, so pop rivet heads are counter sunk...
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All mounted up. Foam can now be glued onto the secondary base and the vinyl glued under it and then it can be bolted down to the main seat base. I have made the holes in the main base for the two M6 bolts 10mm so when upholstery is finally done it can be aligned easily...
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Taillight and number plate light now needs to be set up in a cut out at the seat back. Stay tuned...
Chopit'nrideit... Prof

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