Bultaco Alpina 85 ( 1972) exhaust routing

[jesjra]

Hi

A year after joining this forum and making my first post, I have my Alpina ready to go to the MOT station next week and then start the process of convincing DVLA to give me an original year number plate.

I have been helped with the project and have one question please?

The front chrome exhaust pipe which exits the engine and curls round under the fuel tank comes very, very close to the underside of the fuel tank, within a couple of millimetres, I have some heat reflective tape on the underside of the fuel tank but am concerned about the routing which looks like there is a risk of heat transfer to the fuel tank which cannot be a good thing, any thoughts on how much clearance there should be?

The pictures I have looked at on the internet suggest there should be a gap of about 25 mm, any thoughts welcome?

Regards

Jeremy

[pschrauber]

May be your bike has lost the rubber between gas tank and frame or it was replaced by thinner rubber or the rubber has shrunk in thickness.

 

I would try to place thicker rubber between the gas tank and the frame.

[feetupfun]

I'm wondering if you have the original header pipe or a replica pipe because some replicas are not exactly the right shape.

Whether it is a replica or the original, the under-tank clearance can be adjusted by rotating the front pipe in its cylinder end connection.

Edited May 26, 2017 by feetupfun
better grammar

[jesjra]

Thanks to both PSCHAUBER and FEETUPFUN for your helpful suggestions, I will have a go and let you know how I get on, I will also post a photo.

 

[bult360]

Hi,your pipe should run much closer to the head fins ,looks like you have a repro pipe , I have a model 85 with a repro front pipe that has been tweaked with heat to make it run more parallel to the fins

[71zman]

I had this problem with my M49 and it turned out to be a adjustment issue with the central silencer. To fix it, I took the tank off and removed the rear and central silencers. Loosen the chrome front exhaust pipe and rotate pipe so it is closer to the head fins and tighten the exhaust screw ring. I then worked on fitting the central exhaust silencer to the chrome pipe, It took some "tweaking" to get this to fit correctly. Part of the issue is how the pipes connect (how far the central silencer slides onto the chrome pipe) and part of the issue is adding spacers to the mounting bracket that attaches the silencer to the large engine mounting bolt. One trick is to do the tweaking of the central silencer without the rubber joint.  Once I got the central unit to fit correctly, I reassembled and the space between the chrome exhaust pipe and the tank is adequate

bret

 

[jesjra]

Hi Bult360, thanks for your advice, yes,  I see what you mean having looked at some images on the web.

Being a newbie and lacking engineering skills to boot, I now need to find someone  who I can pay to help me heat and rework the bends of the pipe to get it to run closer to the fins of the cylinder head.

I live on the South Coast of the UK between Brigthon and Portsmouth, if anyone can recommend anyone, it'd be very much appreciated.

Thanks

[2stroke4stroke]

I would try 71zman's wiggle first, it won't cost anything if it does not work.