Topic: HM300's Won't fit -- What The Hell Do I Do Now?

[KC_Northstar]

So I started putting on my brand new set of HM300's.  The left side went on fairly easy, but the right side has problems.
Everything went on OK, but the crossover at the rear of the pipes does not line up.  The top pipe is over almost 3 quarters
of an inch from the bottom pipe.  The clamp on rubber connector is stretched way out of shape. looks like I will have to
bend one of the pipes to get them to line up, but how do I do that without damaging the pipe?   Anyone else had this
problem with new HM300's or HM341's ??
Click on the pictures to enlarge

KC
 

[dhall57]

Since Honda no longer supplies the 300's or 341's must be someones replica brand pipes and specs. are not quite the same standards as the OEM pipes. Johnie a member here has a lot of experience with the original pipes and had some issues with bad chrome on several sets on one of his last CB750 projects. But nothing like the problem you have with your set. So are both sides are out of line the same way? Are the pipes mounted fully into the head as far as they will go?

[KC_Northstar]

Since Honda no longer supplies the 300's or 341's must be someones replica brand pipes and specs. are not quite the same standards as the OEM pipes. Johnie a member here has a lot of experience with the original pipes and had some issues with bad chrome on several sets on one of his last CB750 projects. But nothing like the problem you have with your set. So are both sides are out of line the same way? Are the pipes mounted fully into the head as far as they will go?

These are OEM Honda pipes,  I bought them last year from Honda.  Only the right set fits like this.  Yes they are fully into the head as far as they will go.

[dhall57]

Maybe you just got bad pipe since the left side mtn up fine. Did you buy them from a local Honda dealer near you if so carry it back to them and let them order you another. So the only way to make them line up would to bend the pipe someway.

Do a search about 300 pipes and see what comes up. I seem to remember seeing something about several members a while back having some alignment problems with there pipes also. Good luck KC.

[Greggo]

Something else may be bent.  Has the bike ever been down?

[andy750]

Does it line up at the footpeg i.e. can you slide the 17 mm bolt through both pipes?

Andy

[754]

Is it bottoming on the spigot ?sometimes they get deformed

[74750k4]

Just reinstalled my NOS 341's yesterday. Had no issues the first time I installed them. This time it was a bear. Same side as mentioned above. Inner pipe. Too far forward by 1/2 an inch. Could not install the bolt/foot peg.
After battling it for nearly an hour, it turned out the pipe just needed to be swung under the frame a little bit more, and then all was well!!!

[chewbacca5000]

Is it bottoming on the spigot ?sometimes they get deformed

+1 on this one.  I have battled these before and those spigots need to be just a perfect as the pipes to bolt up easily. 

[Johnie]

Jerry who just put some 341's on his K2 had the same issue same side. I had that issue a year ago with my K3 and the 341's. I had to gently bent the pipe a little. I did the bending with it on the bike a little at a time. I could not get the peg bolt to line up either. After trial and error I was able to get it in line. Just that you have to bend, try it, bend, try it, bend, try it, bend, try it...yes, it takes a while. I think the supplier has issues with the jig on these pipes. That issue along with the poor chrome probably is why Honda has not been making any. Must have been a real headache for them.

[KC_Northstar]

Does it line up at the footpeg i.e. can you slide the 17 mm bolt through both pipes?

Andy

    Yes the bolt goes in ok and I have it tightened up

Is it bottoming on the spigot ?sometimes they get deformed

\

 By spigot, I guess you mean at the head.  Both the inner and outer pipes are about a quarter inch from fully seating.
If I try to get them fully seated then the rear foot peg bolt will not go in. 

[KC_Northstar]

Jerry who just put some 341's on his K2 had the same issue same side. I had that issue a year ago with my K3 and the 341's. I had to gently bent the pipe a little. I did the bending with it on the bike a little at a time. I could not get the peg bolt to line up either. After trial and error I was able to get it in line. Just that you have to bend, try it, bend, try it, bend, try it, bend, try it...yes, it takes a while. I think the supplier has issues with the jig on these pipes. That issue along with the poor chrome probably is why Honda has not been making any. Must have been a real headache for them.

How did you bend them on the bike??  I tried pushing and pulling on both the upper and lower pipes and could not bend either one.

[Johnie]

Yah, I bent them on the bike. I had to remove one pipe to be able to give me enough room to make the bend. I left the spigot end connected and bent it by pulling / pushing on the end of the pipe for leverage. Did not have an issue with chrome cracking as I let the bend happen the entire length of the header pipe. But maybe mine were not as far off as yours. When I had it lined up I had to use a hammer to get the peg bolt through until I could get the threads to catch on the bolt. Then I used the nut to pull it through. What a hassle we should not have to deal with, but what you going to do when you can not get them anymore.

[KC_Northstar]

Yah, I bent them on the bike. I had to remove one pipe to be able to give me enough room to make the bend. I left the spigot end connected and bent it by pulling / pushing on the end of the pipe for leverage. Did not have an issue with chrome cracking as I let the bend happen the entire length of the header pipe. But maybe mine were not as far off as yours. When I had it lined up I had to use a hammer to get the peg bolt through until I could get the threads to catch on the bolt. Then I used the nut to pull it through. What a hassle we should not have to deal with, but what you going to do when you can not get them anymore.

OK, let me get this straight, cause the thought of trying to bend these is a bit scary.
Did you have the pipe fully tightened at the spigot? Did you have to hold the middle and then pull/push.  I guess I cant
quite picture how to accomplish the bend

[Johnie]

Yes, had it tight at the spigot. Not knowing which way you have to bend, but I used the muffler part to hold onto as I accomplished it. The worst case scenerio is if they are that far off that no amount of bending will get it in the right spot. And my bend was just an up and down motion. If your pilot hole for the foot peg is way off that is another issue. But if I read it correctly your peg hole is good but the vents do not line up. If that is the case you may have to do a twist type bend. Maybe on both pipes opposite each other so they mate up. Again, not knowing how far off you are I hope you can get it. These are to dang expensive...

[Johnie]

So here is a question I never really saw here...what happens if you just do not connect those vents together as a last resort? Is there a problem with that regarding back pressure, sound, etc.? I mean you can not really see it that good...just wondering???

[mono]

It would create tuning issues.

Sent from my SPH-L710 using Tapatalk 2

[KC_Northstar]

"But if I read it correctly your peg hole is good but the vents do not line up."

Yes, everything lines up except the vent holes.  After closer inspection it looks like the lower pipe is bent slightly
in toward the bike from the peg hole back.  I'm going to try some bending tomorrow.  These were expensive. 
Cant believe I have to be bending them.

[jerry h]

Hi KC,  I had the same issue, left was slightly off, right side fit terrible.  I think I got the last 2 upper HM341's available in the US.   Both bottoms, I had to get via Ebay.  I originally thought that the trouble was maybe from mixing 3 different runs of pipe, but that upper right was really off.  It would bolt up just fine, till you look at the interconnect in the back, just like your picture.  That #3 pipe isn't bent enough/and or the tube for the bolt isn't welded in correctly.  Maybe by the last run of these pipes the jigs were getting worn out?

My solution was......... GASP ----- dremel some off the tube that the foot peg bolt goes through.  I tried to bend it like Johnie, but chickened out after a few unsuccessful tries.  These darn pipes are worth their weight in gold now, and you have to try to bend them or grind on em??    Not fun.  I was able to grind off just enough, that the rubber is straight enough to be passable.  I try not look at it though, because it bugs me that its not perfect.    I'm sure that miss-bent pipes, and bad chrome is what finally pulled the plug on our mufflers.  Mine would have been sent back immediately if there was an option of getting properly made ones. 

[jerry h]

Forgot, I had to add a washer between the muffler and the foot peg assembly to account for the amount I took off that bolt tube.  Not what you want to be doing at the end of a detailed restoration, but we have no choice at this time.  You can't see it by looking at the bike, so you have to "make them fit".

I'm sure earlier exhaust runs probably bolted up just fine, but since we have the exact same problem, I'm sure now its poorly made pipes. 

[KC_Northstar]

"My solution was......... GASP ----- dremel some off the tube that the foot peg bolt goes through.

Thanks Jerry,  I was just considering the same thing.  I don't know if I could bend them, but I might be able to modify
that tube like you said.  I'm thinking maybe if I grind it at an angle that when the bolt is tightened it might pull it over?
Not exactly sure how to grind it, but I will look at it tomorrow and see what I can come up with.

KC

[754]

Sochiro would have flown over on the. Corporate jet, and kicked the vendors asses..

[phil71]

i have seen those new 300s, with the stamped warning right? I kinda think they sent the tooling to one of their chinese factories for these OEM repops. I've had a couple not fit so good. Here's a link to a very hi-res photo of a bone stock survivor, from a vantage point that will give you an idea of what you're shooting for spacing-wise.

https://www.wetransfer.com/downloads/650a334efa36b01b59694d95d562d68420130525042007/ca9f7d8524d2aab7a0b5f23926d4bc4520130525042007/cc534c

  If it were me, (assuming there's no recourse at the point of sale) I'd  pull the baffle on the one that's furthest out and use a broom stick or something inside. .. run it up to temp, then apply firm,  even pressure. Not excessive. Do it for a few heat cycles. It will take long, but it will give.  You could map gas it, but you'd almost certainly blue those pipes.
 
 

[HondaMan]

Hi KC,  I had the same issue, left was slightly off, right side fit terrible.  I think I got the last 2 upper HM341's available in the US.   Both bottoms, I had to get via Ebay.  I originally thought that the trouble was maybe from mixing 3 different runs of pipe, but that upper right was really off.  It would bolt up just fine, till you look at the interconnect in the back, just like your picture.  That #3 pipe isn't bent enough/and or the tube for the bolt isn't welded in correctly.  Maybe by the last run of these pipes the jigs were getting worn out?

My solution was......... GASP ----- dremel some off the tube that the foot peg bolt goes through.  I tried to bend it like Johnie, but chickened out after a few unsuccessful tries.  These darn pipes are worth their weight in gold now, and you have to try to bend them or grind on em??    Not fun.  I was able to grind off just enough, that the rubber is straight enough to be passable.  I try not look at it though, because it bugs me that its not perfect.    I'm sure that miss-bent pipes, and bad chrome is what finally pulled the plug on our mufflers.  Mine would have been sent back immediately if there was an option of getting properly made ones. 

I've had the same issue/solution: grinding off about 1mm or 2mm on the inside of the left upper pipe's footpeg dowel on my last set was needed. On another set, the chrome was gloppy and too thick on the outside of the same dowel (forgotten now which side it was), had to grind it off where pipe met pipe. Then they lined up OK.

Running without the hose makes a black carbon mess and is surprisingly loud, aside from disturbing the torque (makes less) in the 4500-6000 RPM range.

[KC_Northstar]

Thanks guys,   A Grinding I will go.   Probably wont get to this until tomorrow, so If you hear a blood
curdling scream coming from the direction of northern Minnesota on Sunday, don't be alarmed.
It will just be me realizing I just screwed up my brand new pipe.   

I will let you know how it turns out.

KC