#2 Exhaust fouling frame

[Lobo]

Having an issue with #2 exhaust butting up against the frame in the side-stand area on the ‘750 K2. Everything OEM; and despite loosening all fasteners, and thence retightening with the pipe held clear… it simply resumed its ‘comfort zone’. Which is not mine!

Comments / tips please?

[Laverda Dave]

I had a similar issue with the DSS repro full 400/4 system. No.1 down pipe kept pushing hard up against the sump no matter what I tried. I did the same as you, undoing all the mounting points including the exhaust collars at the head in an attempt to ‘persuade’ it into position. Every time ‘I got there’ doing up all the fixings in sequence to a correct tightness and a bit at a time the final tightening would make it spring back again! Eventually I took everything off apart from No.1 header and used brute force to very slightly tweak the line of the pipe in various places (with my hands and using my knee to support the pipe) whilst keeping it fixed tightly in the cylinder head via the exhaust clamp. It worked with no visible alteration to the line of the pipe and it went into the collector box without any issues but I must have spent 3-4 frustrating hours doing it. Ideally I should have made a template with a coat hanger, filled the pipe with sand and taken it over to the vice to tweak it, problem with that was a very large wodden mallet was close by and I know the frustration would have got the better of me . At least keeping it clamped to the bike allowed me to trial fit the rest of the system in stages and get it right.

I’m surprised you are having trouble with an OEM part although as has been said many times before, OEM is slightly different from ‘Original’ or ‘NOS’. It might be OEM but is the OEM using the same original jigs to make them? DSS and CMS state their systems are a straight fit but I can argue otherwise especially for the 400/4

Keep tweaking it and you will get there unless it is really bad in which case send it back to the OEM. Enough of these sets have been sold so it will be interesting to see if anyone else has had the same issue and how they cured it.

[Johnny4428]

I have a problem with my No2 exhaust pipe up against the oil filter housing. Bloody annoying having to remove exhaust to change oil and filter. 😡

[Oddjob]

Most of these problems end up being bent brackets, if it's not the fault of the exhaust itself. Try removing the hanging bracket and test fitting it just using the head clamp, see if you can hold the bracket against the frame and work out which way bending it would work. The DS hanging brackets for the 500 system are well known for this.

[Lobo]

Thanks gents - my lazy error Dave, indeed all is original / NOS. I reckon it’ll be Ken’s suggestion… it was my next avenue but always hopeful of something easier! Whilst I’m here, given engine movement, what kind of ultimate gap am I looking for… 5mm?
Ta.

[Oddjob]

These engines aren’t rubber mounted like cars and some me later engines. As such there should be minimal movement, it’s clamped very tightly in the frame, so even a few mm should be ok. The more the better of course, try for 5mm and see how you go.

[McCabe-Thiele (Ted)]

Although my 400 had a Motad system I had trouble getting it to re-fit properly after my rebuild using the mount that was in place. I ended up fitting the front pipes into the silencer using a different rear bracket that came with the bike.

I agree that the rear bracket mounting  bracket  is the key to a good fit. If the pipes into the silencer fit is good then it's worth trying to align the rear bracket so it's under little or no stress when it's clamped up.
 

[Lobo]

Ran out of time 1/2 through today, but got #2 pipe off and am struggling to see how to  get the clearance I want - and figure I’m going to have to SLIGHTLY grind it’s ‘hanger hole’ so it butts to the frame off-square…. and ‘tilts’ the exhaust inwards a few degrees.
What’s really confusing me is that I’ve owned / been intimate with this bike and its HM341 pipes 10yrs now, and never been aware of this issue. I stripped it completely down last year, there was no rub / witness markings evident in either the frame nor exhaust - so what gives??? The only 2 things that changed in the rebuild are the newly powder coated frame, and my ‘plastic sleeving’ the footrest bolts as they had excessive vertical slop.

[Johnny4428]

Very little scope for altering on these with the single mounting bolt going through the silencers and bolting through a boss on the frame. No mounting brackets as such that could be manipulated.

[McCabe-Thiele (Ted)]

I agree Johnny iirc I ended up using a stand off spacer as well as enlarging the slots.

[JamesH]

Ran out of time 1/2 through today, but got #2 pipe off and am struggling to see how to  get the clearance I want - and figure I’m going to have to SLIGHTLY grind it’s ‘hanger hole’ so it butts to the frame off-square…. and ‘tilts’ the exhaust inwards a few degrees.
What’s really confusing me is that I’ve owned / been intimate with this bike and its HM341 pipes 10yrs now, and never been aware of this issue. I stripped it completely down last year, there was no rub / witness markings evident in either the frame nor exhaust - so what gives??? The only 2 things that changed in the rebuild are the newly powder coated frame, and my ‘plastic sleeving’ the footrest bolts as they had excessive vertical slop.

Lobo - have you removed/refitted the exhaust spigots that bolt to the head and crush the copper gaskets? A minuscule change in the alignment of these leads to a big change at the exhaust hanger end..   

[Lobo]

Thanks James - yep, I have removed it; the crush washer is crushed evenly. Are you saying that if I set the silencer as wanted, and only then tighten down the spigot (sympathetically) it’ll work out? (have a set of new crush washers at the ready - not keen to use ‘em until I’m certain of a positive result!)

If I understand this correctly, the #2 exhaust muffler connector will subsequently loose vertical alignment with #1 - ie presumably I’ll have to refit / realign #1 exhaust spigot?

(Accepting it’s a different exhaust part #; I looked under my Sandcast and note the pipes well clear of all frame paraphernalia - which only added to the confusion)

Anyways - appreciate this new info and will try again later in the week.

[JamesH]

Was just a thought really lobo.

I'm currently having an alignment issue with a reproduction no.3 exhaust from Busso (thread on the US site). I'm just challenging my own thinking, really, so thought I'd put it out there. The problem with access to the spigot screws is it's difficult to get purchase on them with the exhaust clamping crowns fitted; so playing around is a bit of a bugger - and you don't want to introduce an exhaust leak into the equation once they've been clamped/crushed intiially.

I guess I was just trying to see 'what's changed' with your setup and if that's contributed.

Logic doesn't always seem to apply to these bloody exhaust systems.

[Lobo]

Thanks James. Tbh I’m not having problems with the spigot screws as using a very nice long Allen wrench which fits in between the clamping crown fins.

I’ll play with your suggestion, but basically feel those spigots are engineered to clamp down squarely (against the crimp rings) in order to guarantee a seal. We’ll see… otherwise it’ll be something a bit more significant 😱.

Still struggling as to ‘what’s changed’.
Ta. Simon

[Johnny4428]

Good shout James about the exhaust spigot. Having given a bit more thought into these exhausts fouling frame and engine oil filter housing I wonder if the boss on the silencers are not the correct width which could make it fit badly. In my case I had to pack an extra couple of oversize washers on the inside of frame to take up the slack ad the threads were bottoming out and the footrest on the outside was flopping about still. Think I’ll try the washers between the outside of frame and the inside of the No2 silencer boss.