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Modifying A 4Rt Rear Mudguard To Fit A 315R - How?


givemea5
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On 21/03/2018 at 1:37 AM, oni nou said:

Its a 1mm thick head spacer made from a sheet of alunimimimun.that fits where the head gasket goes. the addition of this between the cylinder and the head increases the combustion chamber size and so decreases compression and therefore lessening the chance of detonation, AKA pinking...... fuel is rated in RON etc ......the higher the RON [eg 98 super unleaded]the less chance you have of detonation of the fuel occurring......  The higher the RON rating the more you can compress it before it combusts without the presence of a spark from the spark plug.

Where could I get the 1mm head spacer? Would a thicker base gasket give the same effect currently got a .5mm base gasket and pinking issues.

What's driving me crazy 

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What difference will altering the port timing make?

On 21/03/2018 at 1:37 AM, oni nou said:

Its a 1mm thick head spacer made from a sheet of alunimimimun.that fits where the head gasket goes. the addition of this between the cylinder and the head increases the combustion chamber size and so decreases compression and therefore lessening the chance of detonation, AKA pinking...... fuel is rated in RON etc ......the higher the RON [eg 98 super unleaded]the less chance you have of detonation of the fuel occurring......  The higher the RON rating the more you can compress it before it combusts without the presence of a spark from the spark plug.

Where could I get the 1mm head spacer? Would a thicker base gasket give the same effect currently got a .5mm base gasket and pinking issues.

What's driving me crazy 

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No I haven't set the squish don't know what is meant to be?

What difference will altering the port timing make?

On 21/03/2018 at 1:37 AM, oni nou said:

Its a 1mm thick head spacer made from a sheet of alunimimimun.that fits where the head gasket goes. the addition of this between the cylinder and the head increases the combustion chamber size and so decreases compression and therefore lessening the chance of detonation, AKA pinking...... fuel is rated in RON etc ......the higher the RON [eg 98 super unleaded]the less chance you have of detonation of the fuel occurring......  The higher the RON rating the more you can compress it before it combusts without the presence of a spark from the spark plug.

Where could I get the 1mm head spacer? Would a thicker base gasket give the same effect currently got a .5mm base gasket and pinking issues.

What's driving me crazy 

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On 3/11/2016 at 8:09 PM, gazza7965 said:

Hi givemea5

 

I did this conversion for my 315 and it does make it look much more modern.It is not too difficult to do but there are some mods needed to make it fit correctly. I will try and detail everything I did:

 

1. Obviously cut down the mudguard, I did this carefully with a large hacksaw blade. You need to line it up by fitting the mudguard to the bike with the 2 mounting holes fitted to the brackets on the airbox and mark where it meets the tank on each side of the new mudguard. Make a template from 2 inch masking tape of the profile of the edge of the fuel tank where the mudguard will meet or the original 315 mudguard front edge. use this as a template to cut across the the 4rt mudguard, this also helps not to scratch the new mudguard when cutting. Once cut you will find you will have to chamfer the edge of the mudguard where it meets the tank as the edge of the fuel tank is angled. (The cut should go through the middle of the two front square vent holes on the mudguard) see picture

2. Drilling the hole to mount the mudguard at the front.- I drilled a 6 mm clearance hole in the centre of the mudguard, 35mm from the front edge once it had been cut. This may need to slightly elongated but not by much to fit perfectly. 

3. Mudguard mounting brackets on the airbox..I found that the original airbox mounting brackets not to be correctly located to make the mudguard sit right. I found that only one of these brackets can be used. To get the mudguard to sit correctly, i swapped the right hand bracket to the left hand side which in effect moves the mounting position up a little. I made a new bracket for the other side, it is not too difficult they are only sheet metal. This bracket is best made once you have the mudguard sitting correctly on the front mounting and the left hand side mounting. This then shows you exactly what shape the right hand side bracket has to be.

4. Modifications under the mudguard. The 4RT mudguard has a plastic plate moulded into the guard towards the front that when fitted, sits on top of the airbox, I think its stops the mudguard flexing downwards when sitting on it. The airbox is obviously different on the 315 so this has to be modified.  I pop rivetted an aluminium plate to the original plastic tab that when fitted gave a measurement of 55mm from the bottom of the plate (where it would touch the 315 airbox) to the underneath of the mudguard. There is also a gap where the underneath of the mudguard meets the back of airbox which if not covered in some way would allow all the mud/water thrown off the tyres to go through the gap and run down on top of the air filter area. I made another metal plate and sandwiched a rubber flap (made from an old inner tube) and pop riveted this to the flange that runs across the middle of the mudguard underneath. This flange must also be trimmed to fit before fitting the plate as it fouls the airbox mounting brackets. Finally glue some expanded foam rubber to the underneath the mudguard with contact adhesive to close the gap completely and allow no mud/debris thrown off the  rear wheel to enter the top of the airbox. see picture.

 5. The front mounting bolt. On the 315 mudguard, the front mounting bolt sits in a recess and the underneath of the recess sits on top of the fuel tank mounting grommet. This is not the case on the cut down 4RT mudguard, which means a much longer bolt is required. I found this gives a problem, when sitting on the bike, the mudguard still wants to flex and put this bolt under a lot of pressure. I got round this by making a new fixing that fixes the fuel tank in position first and then allows the new mudguard to sit on top of this fixing and allows a much shorter bolt to be used to secure the mudguard. This is made from a 10 mm bolt with the unthreaded shaft part cut to a length of 15mm. (This replaces the spacer used to originally fix the fuel tank) Drill through the centre of the entire 10 mm bolt and tap all the way through the 10 mm bolt to a 6mm thread.Thread lock a 20 mm stud of 6mm studding into the bottom leaving around 12 mm of the thread exposed. You then have plenty of female thread on top of the bolt to use to fix the mudguard using a 12 mm long, 6mm button head allen screw. see picture.

6. Finishing touches. Where the 4RT mudguard now meets the fuel tank, the front vent square holes are no longer the same shape. I made some decals that give the appearance that the mudguard shape and appearance has been maintained - see picture.

 

I hope I have covered everything and this makes sense but if you have any questions then please let me know.

 

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Hello gazza7975,

I am planning on giving a 2003 315R a 4rt Repsol make over. Powdercoating the frame, swingarm hubs black and the rims orange. Also using 4rt plastics and Repsol racing decals.

For the orange rims i found out that the color should be RAL2003, what did you use for the black? Should this be matt or glossy?

Is there a certain 4rt Repsol model year of which the decals fit the best on a 315?

Any other things i should take into account when updating the 315?

Thanks in advance.

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