Best way to decoke middle box on a 315r

[jes42]

Just bought a 2004 315r and want to tidy it up and give it a once over. Have fitted some new clutch plates to hopefully sort out a bit of clutch drag and all the usual stuff, oil change, filter, plug etc but I want to repack the silencer and decoke the mid box as it looks a bit gungy!! Whats the best/easiest way of doing it ? Any help greatly appreciated. Also, does anyone know where I might get a "Lampkin Replica" graphics set from? Cheers.

[wherry]

Well I did mine by filling it with some spare petrol overnight and giving it a good slosh around, then leaving it to drain out and evaporate for a few days. If I did it again I'd be very tempted to do the same but with paraffin instead of petrol so it was less of a potential firebomb. After I'd got rid of at least the surface gunge inside I then gave it a good scrape out as best I could and tapped all the bits out. To be honest I'm not sure how much difference if any it's made.

It's difficult to be absolutely definite about it but I think repacking the rear box has had more effect and has softened the power a bit.

Stickers I don't know about but I'd be tempted to give Sandifords a ring. I get most of my stuff from BVM in Stroud - they may be able to track some down.

What clutch plates have you put in it?

[lowbrow]

Hold it flat out down the local by-pass. By the time the smoke screen you lay down is sufficiently thin that other road users are able to see to overtake you the middle box should be nice and clean

[monteberg]

remove it from bike bung up one end (potato works good)stand it up vertical and fill with a strong caustic soda mix and leave 24 hours a good rinse out with hose pipe N:B Ive used this many times in the past on road/race 2 stroke pipes and it works but i can't stress enough how dangerous this strong alkaline chemical is, caustic soda (sodium hydroxide) will dissolves all the oily gunk in your exhaust but it also dissolves skin and flesh in seconds and if you get in your eyes you are in big trouble .wear chemical gloves apron and googles or better face mask and have a bottle of vinegar and running water at the ready ,i once spashed a bit on my thigh (through jeans )emptying it out after sitting in pipe overnight and i had the running hose pipe on it in about ten seconds and it still burnt me ,if you splash yourself throw some vinegar on it(the acid vinegar helps stop the alkaline burning ya ,then get under some running water ,if you choise this method of decoking your exhaust, be careful,do it somewhere you can prevent anybody else touching it ,keep children and pets well away ,ps the drain unblocker and oven cleaners in the shops are the same caustic soda(sodium hydroxide)but more dilute and nowhere nearly strong enough have fun ,IT WORKS, but be CAREFUL oh nearly forgot it also dissolves aluminium (its used to etch it and also used to prepare it for anodising so you really dont want to be splashing on your montesa frame or tail pipe etc ...by what premix oil are you using and what ratio getting ratio to riding style dialled can help prevent build up of gunk

[wherry]

The middle box is aluminium too....

Edited October 8, 2010 by Wherry

[monteberg]

The middle box is aluminium too....

not a good plan to use caustic then wait for the wife to go out and bung it in the oven and cook it out (remember to use the extractor fan)

[martin belair]

This has been discussed on this forum before. You may want to search for it.

Cut it open, re-pack it with Silent Sport packing and weld it up. I have had it done several times by Mike Komer at the Tryals Shop. This method yields excellent results. I have seen it done by the factory boys as well, when they were on two strokes.

Mike used to grind the seams and split in half, but the last one he did, he cut a window open on top and bottom to access the packing.

These other methods sound dangerous and I don't believe that they will be as good as new packing.

[jes42]

Thanks guys. Used a combination of all the advice - bunged up the end and soaked overnight in paraffin, then after letting it dry out blew it through with compressed air, loads of crap came out so it must be an improvement. The clutch plates are the apico ones which are slightly cross-hatched to allow a bit of oil to stick and hopefully cure the drag. Not tried it yet but will post on here with the results. Out for a practise on Wednesday so fingers crossed!!!

[caravan_monster]

This has been discussed on this forum before. You may want to search for it.

Cut it open, re-pack it with Silent Sport packing and weld it up. I have had it done several times by Mike Komer at the Tryals Shop. This method yields excellent results. I have seen it done by the factory boys as well, when they were on two strokes.

Mike used to grind the seams and split in half, but the last one he did, he cut a window open on top and bottom to access the packing.

These other methods sound dangerous and I don't believe that they will be as good as new packing.

Hi, I can't find anything about the 'window' method with the search facility. It sounds like a better option than cutting the seams because it avoids any potential misalignment problems, but does anyone have any info. about best placement of the window ? Judging from the weight of the component, I'm guessing it might be complex inside and I want to avoid unnecessarily damaging anything when I open it up. Would a pop riveted and silicone sealed piece of aluminium over the windows be viable repair, with future cleaning and repacking in mind, or does it need to be welded ? Is Silent Sport packing different from the normal stuff ? Not heard of it before. TIA for any advice, Tom.

[bigshineybike]

Mine is a 348 so sorry if this is not appropriate to this thread but its useful I think.

My 348 was very noisy in an unpleasant way being very tinny/tingy rattly etc.

The back box I know people repack and swap for exotic alloy items.

So I repacked my back box and even tried an alloy exotic but still the bike sounded horrible and the fibreglass of the tank cover where it rubs on the centre box was burning.

Mick at Tricky trials suggested that my centre box packing has all blown out and that the perforated tubing inside has come adrift.

shaking the pipe reaveled he was correct.

I needed to open it up and have a look.

The decision then cut the seams or make a window?

well the seams are very long, there are the pipes at either end and some of the partitions inside are welded across so it will not simply fall open.

On my 348 I cut a window with a 1mm sliting disc fitted in my angle grinder.

I have paneled over the hole with an over sized peice of aluminium. As the metal of the silencer is so thin, self tapping screws would not tighten so I have used pop rivets.

Mine does blow a bit so I like your silicone idea.

My bike however runs much better now and is quieter with a much more satisfying exhaust note.

Edited October 17, 2010 by bigshineybike

[caravan_monster]

Good to know it worked on the 348 - my 315 is similarly noisy as it is. What function does the middle box perform ? Is it just an additional silencer, or does it manipulate the exhaust pressure waves a bit like an expansion pipe on an 2t enduro or motocrosser, to give the desired engine characteristics ?

When I cut windows into the 315 middle box, will I just find a perforated tube and packing, or are there other parts in there ?

[caravan_monster]

I took some photos to show how I went about cleaning and repacking

I cut the windows here:

and here

I used the drill (with depth gauge) and hacksaw instead of cutting disk to cut the windows, to avoid damaging the perforated tube inside. A hook was made from stiff wire to pull out all the old packing. Once the packing was removed, I heated the inside of the perforated tube with the gas burner. The oily gunge caught fire and was left to burn out. It was then easy enough to shake the soot out and get everything reasonably clean.

It was then repacked, taking care to get packing into all the corners:

Then a paper template was used to get the right shape for the plates to go over the windows. Silicone and pop rivet:

Hope this helps

[widrace]

Excellent post Tom! Tidy workmanship as well - kudos

A few questions for you:

1) On the inlet side patch, you took out some of the radius. Is this necessary?

2) Does the tube come too close in proximity to the body to use a disc for cutting in these areas?

3) What would you have done differently? Alternate locations perhaps?

4) Is there anything going on in there besides the tube?

5) How much time was on your silencer, and how solidified was the packing?

6) What shape was the tube in and is it captured in the same manner as the rear silencer?

7) Have you noticed a performance change at all?

Thank you!

[caravan_monster]

Excellent post Tom! Tidy workmanship as well - kudos

A few questions for you:

1) On the inlet side patch, you took out some of the radius. Is this necessary?

>not entirely, but it did make it a lot easier to get at all the packing at the inlet end.

2) Does the tube come too close in proximity to the body to use a disc for cutting in these areas?

> Yes. I gang drilled the corners of the windows and cut between with a hacksaw blade. It wasn't that time consuming - it took much longer to get out the old packing.

3) What would you have done differently? Alternate locations perhaps?

>Probably stay the same. Windows are needed at both ends and on both sides to be able to get at all the packing.

4) Is there anything going on in there besides the tube?

>just the tube

5) How much time was on your silencer, and how solidified was the packing?

>not sure, the bike is new to me (2000 model). I suspect it had been split along the seams and re- packed previously because the welds don't look very 'factory'. The packing was oily, but this may well be because the timing and / or jetting is off and the bike doesn't run as crisply as it should.

6) What shape was the tube in and is it captured in the same manner as the rear silencer?

>The tube is in good condition. I think it is the same as other silencer, but not 100% sure because I couldn't see much inside

7) Have you noticed a performance change at all?

>don't know yet. The chassis is still in pieces in a box waiting for me to put it back together !

Thank you!

[widrace]

I was initially under the impression that you were able to get at all the packing via the two window areas shown in the pics. Does your finished product have 4 windows, or did you go with two and leave some packing behind?

Cheers to ya...