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Author Topic: Honda CB450 K5 Cafe Racer.. ish  (Read 9704 times)

Offline bezugo

  • Posts: 53
Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #30 on: Aug 14, 2016, 18:09:48 »
Thanks!

What may be the consequences of worn rings?  From what I remember it's not a big deal. Just loss of power and oil consumption.
Am I right?  These engines are new to me.

What about those O-rings?  Where are they supposed to go?  That may be my leak..

Offline Flugtechnik

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  • My bike is not transportation, it is a respite
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Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #31 on: Aug 14, 2016, 19:40:23 »
First, the carbs:

You replaced all of those things in the pic except the o-rings?

The larger of the o-rings goes on the bowl drain screw.

The smaller of the o-rings goes on the air/fuel mixture screw.  You also have to have the spring and washer on there in the correct order.  First you put the spring on, then the washer, then the o-ring.


As for the oil from the exhaust:

There should be abolutely no oil in your exhaust.  If there is you have a problem.  Was the oil coming out where the exhaust attaches to the cylinder head?  Are you sure it wasn't coming out from between the cylinder head and cylinders near the exhaust? 
« Last Edit: Aug 14, 2016, 19:50:25 by Flugtechnik »

Offline bezugo

  • Posts: 53
Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #32 on: Aug 14, 2016, 20:36:32 »
Oops!  Guess I didn't do everything right.
There was no washer or o-ring between the spring and the mixture screw before, so I didn't know they should be there.

I didn't use any washer other than the one that goes with the float valve and didn't use any O-ring.
The main jet was changed by the one with the same number (size?) 145.

That may very well be my air leak.

The leak is almost 100% sure from where the exhaust attaches to the cylinder head, but tomorrow I will make sure.
What are the consequences of both cases? Solutions?

Offline Flugtechnik

  • Posts: 3026
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Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #33 on: Aug 14, 2016, 21:12:12 »
Take a look at the parts diagram and make sure the carbs are assembled correctly.  Did you use all of the parts in the rebuild kits?

http://www.partzilla.com/parts/search/Honda/Motorcycle/Models+with+no+year/CB450K5+A/CARBURETOR/parts.html


The smallest washer goes on the air/mixture screw, one goes under the float valve fitting and the last goes on the silver plug that you can unscrew on the bottom of the carb.




Make sure the old washer and o-ring are not still stuck down in the hole.





I just rebuilt my carbs a few days ago.  Here are all the parts.  Should be the same as yours.

« Last Edit: Aug 14, 2016, 21:23:00 by Flugtechnik »

Offline bezugo

  • Posts: 53
Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #34 on: Aug 14, 2016, 21:34:58 »
I didn't use all the parts. The o-rings and washers were left out because I didn't know where they went. Only used one washer on the float valve assembly.

I'm guessing the o-ring and washer are still in the hole...  If so, they're probably not doing their job that well.. being 44 years old.

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Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #35 on: Aug 14, 2016, 21:59:28 »
The washers usually come out with the spring but the o-rings can tend to be sticky in there. I use a set of picks from harbor freight they cost about $3 and are pretty useful  when it comes to cleaning small parts.
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0 - Sold
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0 - Sold
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
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Offline Flugtechnik

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Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #36 on: Aug 14, 2016, 22:10:41 »
If oil is coming out of one of the exhaust ports, there are three possibilities I can think of.

1) The piston rings in that cylinder are very worn or broken and are allowing oil past and into the combustion chamber and is then getting spit out.  There must be a lot if it is not getting burned.

2) You have a very leaky valve guide/valve seal. It is letting oil leak down into the combustion chamber.  There must be a lot if it is not getting burned.

3) Your cylinder head is cracked around the exhaust port somewhere.


Are you sure it is running on both cylinders? Are both exhaust pipes getting equally hot?  It will continue to run on one cylinder, just not well.

Offline bezugo

  • Posts: 53
Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #37 on: Aug 14, 2016, 22:27:54 »
I will remain optimistic and hope for just worn rings. Wouldn't broken rings make a bad noise?

I read somewhere that it could be possible that the air/fuel mixture is too rich (which would explain why closing the choke only stalls the engine) and it could be spewing unburnt fuel mixed with some oil.

It's just that for all I've read, i still don't get why it's stalling when i close the choke. It should help with cold starts right?

Offline bezugo

  • Posts: 53
Re: Honda CB450 K5 Cafe Racer.. ish
« Reply #38 on: Aug 14, 2016, 22:30:14 »
It is definitely running on both cylinders with similar compression (tested with hand in front of muffler).
Temperature i don't know. I'm sure both will burn my hand.

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Honda CB450 K5 Cafe Racer.. ish
« Reply #39 on: Aug 14, 2016, 23:28:20 »
You need a compression tester to test compression. The exhaust won't tell ya squat. You can pick one up at any auto parts store for around $25, it's a great tool to have if you're working on vintage bikes.

Choke is for cold starting only as it enriches the pilot circuit. The bike should stall after running choked for a bit, that's normal.


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« Last Edit: Aug 14, 2016, 23:30:05 by adventurco »
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0 - Sold
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0 - Sold
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0
'97 BMW F650st - http://www.dotheton.com/forum/index.php?topic=75732.0