Any experience with changing exhaust on a VFR750F J/K model

[rc24dk]

My VFR is a 1989 RC24. While it has many similarities with earlier model it differs in several ways when going into details. Many detail differences I have learned about here and some differences are easier to see, such as wheel sizes, front fork, instrumentation, fairing and exhaust. For years I was fearing that the day my downpipes wore out would be the end of my days of motorcycling so I started to look around for replacements. Some years back I replaced the collector box when these were available at David Silver Spares, so this is in faily good condition.

 

Unfortunately very few - if any at all - made aftermarket replacements for the pipes and if so they were discontinued decades ago. In my search I was lucky to find a set of original downpipes in a serviceable condition which I immediately bought and stored in my secret vault until the day ...

 

I am now in the Gun-gum phase of my old (34 years, as a matter of fact) down pipes so I am thinking this swap may be a project for the coming winter.

 

If any of you have some experience with replacing downpipes on a J/K I will be grateful if you will share it here.

[Captain 80s]

Paging Fastdruid, paging @Fastdruid.  Please pick up the red courtesy phone.

[Fastdruid]

41 minutes ago, Captain 80s said:

Paging Fastdruid, paging @Fastdruid.  Please pick up the red courtesy phone.

I'm coming buddy! 

 

If your bike is a low mileage garage queen that has never seen the rain this may be easier for you. 

So, first off ignore the HBoL where it says you need to remove the engine. You don't and with the age of these it's a risk. Particularly the rear lower bolt which has a far too small hex in it and runs through a U in the bottom of the engine so corrodes in place. I've had to cut two off in the past but you could get replacement bolts then!  

 

Next up, be utterly prepared to deal with snapping exhaust studs. They're piddly little M6 ones.  If you plan on doing it this winter then start spraying them with penetrating now! 🤣

 

Ignoring the parts that are NLA, my personal minimum shopping list for this would be

 

18291-MN5-650 (exhaust gasket) x4

90304-438-000 (front nuts) x4

 

Unfortunately when I did mine I believed the HBoL so took the engine out...🤣

 

After the event I realised this wasn't needed. It's still a massive pig of a job though even without taking the engine out. 

 

So, here is how I would do it if I was to do it over again. 

 

-1) Get the bike properly hot and then spray all the exhaust bolts/nuts with proper penetrating fluid (ie not WD40) at least a week before. Keep spraying them every day until you're ready. The exhaust studs particularly the fronts where they get sprayed by water from the front wheel will snap for fun so everything you can do to prevent that helps. 

0) Put the bike on the main stand on a 2x4 or similar (and the same under the front wheel) to give some extra height. 

1) Remove seat, tank, side fairing panels, belly pan and all rear plastics (inc tail light), unbolt and remove the silencers and the collector. Undo the front to rear header clamps. 

2) Remove battery, disconnect wiring from ECU, reg/rec, pickups,  starter solenoid, fuel pump relay and rear coils (note which way they're connected)...but if you forgot then bottom connector on bottom coil is black/white, next one is red/blue, bottom connector on top coil is black/white then top is blue/black. Remove the rear coils. Remove the pipe to the rad from the coolant tank. Disconnect the hose from the carbs to the fuel pump. 

3) Remove the loom from the subframe up until where it meets the frame, remove the top bolt for the rear brake master cylinder, remove the rearsets and remove the subframe. 

4) Remove the rear wheel. 

5) Unbolt the top shock mount, the remote adjuster, the linkage bolt (the one to the frame) and the two special bolts either side of the swingarm and remove the swingarm with the shock, move the chain over it so you don't need to remove that.  

6) Remove the remains of the shock heat shield (it's inevitably a rusty hole by now). 

7) Loosen (don't remove) the rear engine bolts (the ones that go into the back of the rear head) and then remove the heatshield plate they hold on. 

 

Spray all the exhaust nuts again with penetrating fluid. 

 

At this point it's time to actually tackle removing the exhausts. Now personally I would be very tempted to go straight for cutting the front nuts off. two slits either side with a Dremel or similar then split them. It massively de-risks the chances of snapping a stud. If you decide not to then I would go *straight* for lots of heat on them, get them hot and hope they either unscrew from the head or unscrew. If they don't and snap....well you're now going to have to drill out and re-tap the remains.  

 

Once you've got the fronts out then you can remove the front downpipes from the rears. 

 

Next up is the rears, you should be able to get an 10mm socket on to the end of the nuts using a massively long extension going through the back of the frame. 

Once they're undone you should be able to wiggle the rear exhausts out, it can be done but it can take some wiggling and having extra ground clearance helps (hence why starting off with the bike raised). 

 

Remove the exhaust gaskets (they're particularly hard to see in the rear ports), stick the new ones in the ports with a blob of grease to hold them in place, wrangle the newer ones in, fit the front downpipes and then tighten the nuts on them. Make sure you don't get the left and right front downpipes mixed up (DAMHIK!)

 

In classic HBoL fashion, assembly is the reverse of disassembly...

 

1) Refit the heatshield plate between frame and engine, tighten the rear engine bolts (the ones that go into the back of the rear head) to sec. 

2) Refit the heatshield plate between exhausts and shock. You may want to consider making a new one as it's nothing special but rusts away and does protect the shock from heat.

3) Refit the swing arm, don't forget to loop the chain through first! Bolt the linkage and shock in. 

4) Refit the rear wheel

5) Refit the subframe (and rearsets) and fit the loom to it. 

6) Refit the rear coils, connect everything you disconnected back up again. Refit the battery. 

7) Refit the tank, connect up the fuel pump to the tank and to the carbs. 

8 ) Refit the collector. 

9) Refit the exhausts. 

10) Refit bellypan, side fairings, seat plastics/tail light and seat. 

 

Start her up.

[Captain 80s]

That's about the quality (and quantity) I expected.   But the line for the courtesy phone is fucking long and people are pissed.

 

My one comment is in agreement...

 

Starts soaking EVERYTHING now in penetrating fluid. Often and liberal.  Maybe apply a little heat now and then.  And WD40 is not penetrating fluid, it smells too good.

[Fastdruid]

The reason why I replaced mine...

 

Now technically it's probably possible to do things without removing the subframe. You'd need to loosen the bolts, undo two, pivot it to remove the shock and then almost certainly need to remove the swing arm but you could probably have enough access when you've removed the header tank and coils. 

 

 

Equally you can do things with the swingarm in...but honestly I'd remove it. Once you're that far in it's only two more bolts and gives you more room!

 

 

 

 

 

Don't be an idiot and fit the front downpipes the wrong way round... They should sit with the pipes parallel under the engine, not like this! 

 

 

Anyway, good luck. It's again a pig of a job and not made easier by the M6 studs made from the finest cheese metal. 

 

 

 

[Fastdruid]

8 minutes ago, Captain 80s said:

Starts soaking EVERYTHING now in penetrating fluid. Often and liberal.  Maybe apply a little heat now and then.  And WD40 is not penetrating fluid, it smells too good.

 

+100000

 

WD40 is great stuff. Certainly better than nothing but it's not penetrating fluid. 

 

Best penetrating is meant to be 50/50 acetone and ATF. Although I use plusgas personally. 

 

 

[Fastdruid]

I should add I presume you have the Official Honda service manual and FJ/K supplement that is floating round the web? If you don't then send me a PM. 

[rc24dk]

Thank you very much for the thorough description and good advise. Seeing such new downpipes almost make me tremble and feel warm inside 😁

 

The appearance of the rear down pipe looks familiar, except that the (at this stage) leaky zone is where the pipe from the front joins the "Y" although not quite as bad. I have a gun gum repair holding fairly well - at least the remains of this season. In any case it sounds like its soaking time and if the front nuts are nice and come loose a little copper grease to have it stay nice.

 

This is not going to be sunday morning in the front yard. From the extents of the job I will - besides having replacement parts - start looking for a nice room where I can do this without stress, as it may be a project taking a few weeks if I do it myself.

 

Again, thank you very much 👍

[St. Stephen]

On 9/28/2023 at 2:23 PM, Captain 80s said:

Paging Fastdruid, paging @Fastdruid.  Please pick up the red courtesy phone.

 

My confidence in Captain 80's limitless expertise has been shaken to the core. Everyone knows the courtesy phone is white.  😉

[rc24dk]

The red phone may refer to the hotline. To anyone old enough to know what that implied. Considering a late 1980's bike a red phone is apropriate.

[Captain 80s]

18 minutes ago, rc24dk said:

The red phone may refer to the hotline. To anyone old enough to know what that implied. Considering a late 1980's bike a red phone is apropriate.

 

Hah!   I actually contemplated what color, and I chose red for those reasons.  White would be for the general public.

[Fastdruid]

9 hours ago, rc24dk said:

Seeing such new downpipes almost make me tremble and feel warm inside 😁

 

I was massively, massively lucky and picked up a brand new, unfitted Motad set of downpipes off ebay for the laughable sum (from memory here) of £36...back when Motad were still a going concern and were selling each half of the system for about £330! It was missing one of the header clamps, cost me about something like £18 just for that!

 

Picked up the other half of the system as a factory second (It did have a Motad silencer when I bought it but with original downpipes and someone had modified the Motad so it no longer fitted the Motad pipes).