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Discussion Starter · #1 ·
Hey Guys! I’m having a mind boggling issue with an almost completed 450k5 cafe build and am fresh out of ideas on how to handle it. I’m hoping one you have come across this before and maybe can give me a clue.

The bike was not running when I picked her up in January, and this past weekend I finally got to start her up for the first time! That feeling just never gets old! Anyway, once I got the motor all dialed in, I hoped on and tried to take her for a spin around the block. But something isn’t right…

It’s idling perfectly at about 1100rpm, but when I put it in 1st gear and rev the throttle, she won’t come back down from 3k or so rpm, just continues to rev high. If I release the clutch a bit she won’t move at all in 1st gear just winds out and continues to rev high. However, if I shift into 2nd gear and slowly release the clutch, I can take off and eventually progress to 3rd and beyond without issue. No matter what gear I engage while standing still, if I hit the throttle she will not come down from the high revs until I release the clutch while in gear. But while out of gear I can rev the throttle and all is good…

I rebuilt this motor with new pistons, valves etc, but never touched the clutch or tranny. At this point I’m starting to think new clutch plates and springs might be in order… or is it possible my transmission is smoked?

I’ve checked the clutch cable and re-adjusted it, sprayed starter fluid around the carbs to see if it was a leak, it’s good, also checked the carb slides, they’re moving as they’re supposed to. I’m no mechanic but can navigate a motor ok, am I just missing something here or do I have a real issue? Thanks in advance gents!
 

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I have nothing to offer? This is quite a brain tickler here... At first I thought it sounded like a carb synch issue until I read the first/second gear thing.. Hmmmm.... Have you checked the operation of the advance unit?

Someone will chime in soon enough with some ideas for you.


GB :mrgreen:
 

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Discussion Starter · #3 ·
Hmmm, the advance unit is a thought..it’s new but was kind of a bitch to get the trimming right, It’s actually at it’s fullest clockwise position now…might have to pull that off again and play with it some more…

What about carb floats? I set them as recommended, but on this build the rear of the bike is raised a bit more than stock and as such the carbs sit at a bigger angle… don’t think that would affect the shifting at all, but could that cause the revs to stay high? Hell maybe I have multiple issues…
 

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I think maybe you have several unrelated issues here.
A 450 with carbs that act like that invariably has a "synch" problem.
Try the procedure posted here in the 450 section.
Though rarely encountered, tight intake valves could also cause it to hang up like that. Use 0.002", not the value the manual lists.

Though you didn't mess with the clutch or tranny, the shift shaft itself may be messed up.
The spring loaded detent levers on the end of the shift shaft (behind the clutch) are notorious for causing shifting problems......
There's also a circlip and washer supposed to be on the left side of the shift shaft (behind the counter sprocket) - if they're missing. lateral play in the shift shaft can also cause problems.

Not quite sure what you mean by having the advancer "fully clockwise" ????
 

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Discussion Starter · #5 ·
Hey thanks Bill! You may be absolutely right about various unrelated issues.

I’m pretty sure I have the carbs synch’d very close, I used this exact procedure and it does feel and sound dead on!

So the manual calls for a 0.0012 valve clearance, are you saying go with 0.002 just on the intake and leave the exhaust side at 0.0012?

The circlip and washer are in place but if I recall there may have been a slight play in the shaft which I wrote off as normal. Guess I’ll check that out for starters.

What I meant to say is the points plate is at it’s fullest clockwise position. I’m going to pull that as well and check the advance unit tonight.

At this point I t sounds like I may have to run checks on nearly everything again and try and pin point these bugs…
 

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FlaTonR said:
Hey thanks Bill! You may be absolutely right about various unrelated issues.

I’m pretty sure I have the carbs synch’d very close, I used this exact procedure and it does feel and sound dead on!

So the manual calls for a 0.0012 valve clearance, are you saying go with 0.002 just on the intake and leave the exhaust side at 0.0012?

The circlip and washer are in place but if I recall there may have been a slight play in the shaft which I wrote off as normal. Guess I’ll check that out for starters.

What I meant to say is the points plate is at it’s fullest clockwise position. I’m going to pull that as well and check the advance unit tonight.

At this point I t sounds like I may have to run checks on nearly everything again and try and pin point these bugs…
Use two thousandths all the way around on the valves. Racers like Team Hansen go up to 5 thousandths or even more on their 450 engines. The book value is totally unrealistic, the feelers are like tin foil, and there's just zero margin for error. Not many of us could expect to get it right at the book value (including myself, and I've done it a lot).

The points plate needs to be pretty much centered, as pictured - too far in either direction, and something is amiss. Maybe you got the advancer cam 180 degrees off when you put it back together....
Try using the procedure here -
http://www.hondatwins.net/forum/viewtopic.php?f=18&t=883

Again, those spring loaded detents on the end of the shift drum are problematic with 450's.
 

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Discussion Starter · #7 ·
Excellent advise! I actually set the valves to a tight 0.0015 since that was the lowest my feelers went. But I did notice a louder tapping in this motor vs. my other 450, which is at a tight 0.0015 as well... I think I'll go ahead and clear them to 0.002 per your suggestion.

Also GREAT step by step on the timming! Hadn't seen that one before, but will follow it through when I get home tonight!

If after I dbl check all this and still have the shifting issue, can I get to the detents by removing the clutch plates, or would I need to break the case open?
 

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Both wheeled detents are outside the main cases, but inside the large right side engine case cover..... You should be able to see them without removing the clutch-pack....(they are in the upper rear bump on the left as you look at the bike from the right side)... However, you will need to remove the oil filter/clutch/oil pump to work on them....
 

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You probably will have a bit more noise at 0.002", but it's liveable. And it makes the parts last a lot longer, improves oiling, blah, blah.....

A running 450 is a symphony of noises, get used to it...........
 

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Discussion Starter · #10 ·
Well, I did some troubleshooting last night and as it turns out I did in fact have two unrelated issues. Both were somewhat my fault. :oops: One was an easy fix the other not so much!

So the high revs were caused by the clutch cable rubbing up against the inside of the left carb when I pulled the cluctch in causing it to not allow the carb arm to sit back in it’s natural position. DOTE! Enter tie-wraps, hi-rev problem solved!

The shifting on the other hand will be a bit more involved to fix.

The problem is being caused because the splined end of the gear shift spindle has about half of the spines that hold the shift lever in place chewed off. I knew this when I was putting everything back together but thought that if I really tightened down on the shift lever it would be ok with the remaining splines. Guess not! It has play in there and doesn’t allow 1st gear to fully engage. Again, DOTE!!! Since I have to replace it anyway, I tried drilling an 1/8” thorough the lever and the spindle and putting a pin through it to hold it in place. But the torque of shifting tweaks the pin and causes about the same amount of slop. No fix!

So looks like I’m in the market for a new shift spindle. If anyone has one they can part with, please let me know how much.

Also, I need someone to make my day and tell me that I DO NOT have to pull the motor back out of the frame to replace it. Do I?
 

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No, you won't have to pull the motor to replace the shift shaft.
But you will have to drain the oil (don't be tempted to re-use it, even if it's brand new), pull off the clutch cover, oil filter and pump, and the whole clutch.
The shift shaft then pulls out through the right side - don't forget about the circlip and washer on the shift lever end. Don't lose that washer, it's special and no longer available. The circlip is nothing special at all.

There's supposed to be a little clip that holds the clutch cable out of the carb flipper's way - it goes on one of the top tappet cover bolts on the intake side there (2'nd one from the outside).
You're ahead of the game - at least you did route the clutch cable on the inside of the left carb apparently - most folks leave it on the outside of the carb.....

Post a photo of your shift shaft - I may have one.
 

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Discussion Starter · #12 ·
That'd be great if you had one Bill! I already did a search and cannot find anything.

I posted this fische shot on the parts section...if you need an actual picture I can shot one tonight when I get home.

viewtopic.php?f=13&t=1698
 

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FlaTonR said:
That'd be great if you had one Bill! I already did a search and cannot find anything.
I posted this fische shot on the parts section...if you need an actual picture I can shot one tonight when I get home.
I need an actual photo of the entire shift shaft, especially the articulated end behind the clutch - there were several variations.......
 

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You drilled the "pin" the wrong way!....You should have drilled parallel to the centerline of the shaft, right at the joint...In essence, creating a "keyway" or one large spline..... You may still be able to do it, but the hole through has weakened the shaft, so keep looking for a new one...... At least you'll be able to ride in the meantime.
 
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