Newbie about to start my first build - '82 Honda CB450 Nighthawk

Yes sir, I let it get nice and warmed up first and made sure I held the throttle all the way open. I also replaced the plugs and gapped the new ones. I still need to replace the plug wire caps and check the valves, but I'm started down the path.
 
very well done the numbers you came up with already are normal ......if they weren't cv carbs or if you held the vacuum slide open the numbers may be even higher... having them within 3% of each other and 150 with the carbs on is golden,now you can be confident in getting a tune on the motor
 
Sounds like a winner to me! I'm going to check the valves and start looking for a rebuild kit for the carbs. I hoping that getting them back in shape will get rid of the problem with it not being able to rev over 3500 rpm. I also want to check the air filter and make sure there isn't a squirrel nest or something in the air box, lol. I checked the oil and it looks brand new. Anybody have any other suggestions?
 
i am not familiar with the ignition cdi but does it use a mechanical advancer ?
anyway there shoild be a way to test the timing with a light and then when you rev up the engine you should be able to observe the timing advancing
the factory service manual would cover that if so
if the timing is not advancing it will kill performance
 
Thanks for the info XB. I just downloaded a service manual for it so I will look in there at the trouble shooting tips and also at how to check the timing.
 
Great start and the right attitude. Couple of thoughts in no particular order:

Plug wires on many bikes are sealed into the coil and are not replaceable. If yours are like that, just trimming a 1/4" off like XB suggested is all you can do. If they have replaceable wires, you could fit new HT leads (plug wires).

Carb kits are typically a waste of money because teh jets and needles are often not as well machined as OEM manufacturers. You mentioned a spare set of carbs. I would guess that the PO either bought them to fit and never got around to it, or swapped them out and it didn't fix the problem.

That tends to suggest that the problem may be in the ignition timing as Xb mentioned. Check the Service Manual to see how to check the timing and use a test light to see if the timing advances as revs rise. If it changes as revs rise, that's not the problem.

Check the air filter is clean - no rodent nests or mud dauber homes in there. Another thing to check is the mufflers for blockage. A simple check is to remove them, fit ear plugs and run the bike for a few seconds to see if it revs OK. If so find a way to clean the mufflers and re-fit them.

Back to the carbs. If the spare set are OK, I would strip and clean them. Keep parts from each carb in different containers. I use a collection of cheap Walmart or grocery store baking trays to put things in as a I strip them, but cleaned out margarine tubs or deli containers or TV dinner containers all work. Just take your time and remove all the jets but leave the flap valves on the shafts. Don't remove the two screws that hold the choke plate or throttle valve to its shaft. You will probably want to leave both crabs connected to each other and remove just the top and all the jets- be sure you take notes and pictures so they go back in the right holes and check a parts list in case teh PO stuffed that up.

I read that people are looking for a 16113-MC0-305 needle for some reason. It's marked 61c and nighthawk guys online think it's the best one to fit. New jets should be available from your dealer or a jet place like Jets R Us.

http://www.hondatwins.net/forums/63-fuel-supply-carburation/21500-1982-honda-service-bulletin-450-drivability.html
 
Thanks Teazer. Yeah, I had thought about just replacing the entire plug wire but when I looked last night I saw that I have the type that are sealed into the coil, so I'm planning on getting some caps and trimming the wires like XB mentioned.

I'm also planning on picking up a timing light and reading up on how to check the timing. I seem to remember that if the timing on an engine is off that it will begin to run rougher as the revs rise until it finally dies. This may be incorrect or my faulty memory so I definitely want to check it. In this case the engine revs nice and smooth up to 3500 and then once you pass that its like it just chokes and dies which is what made me think it might be the carbs.

I meant to check the air filter last night but was focused on the compression and forgot to do it so I will do so tonight.

As far as the carbs go, there are two extra sets, one of which I think are the originals since they are painted black like the engine, but I'm not sure what condition they are in or if they have been cannibalized in the past. If so can I take parts from the various sets to make one good set? I have seen a lot about using a sonic cleaner on them. Would that be the best way to go?

Oh, and thanks for the link
 
Your timing is completly controlled by the CDI, can't be changed, there is no mechanical advance, the timing light will tell you if it is right or not, if it isn't you will need a new CDI, that is one of the few things that a bad CDI will cause is the not reving past XXX RPM, it is usually 3-4K or 6-7 K depending on how fried the CDI is, good news is I believe there is aftermarket CDI's available for this bike as it is the same CDI as 4-5 other Honda's of similar vintage. I used to have 3 but I gave my last one away to a member here about a year ago. If your timing checks out, it is fuel/carb or coil related.
 
Thanks Maritime, and everyone else, for the great info. Yall have made it much easier to get started and made this a much less daunting project than it seemed at first. I think my wife still thinks I'm crazy though, lol.
 
if it cant be checked just do all the other stuff and see how she runs
process of elimination will have to skip over timing for now but should be able to out it as an issue further down the line
 
XB that was my thought too about skipping over it. I did find some methods to test the CDI/ignition coil so I'm going to try those. From the indicators I've read and from what y'all have said here I'm thinking it's probably bad and I've already started the search for a replacement. My choices seem to be either a new aftermarket that isn't an exact fit and fab up a bracket for it or a used original equipment one. Right now I'm leaning toward the new one and new plug wires.
 
xb33bsa said:
if it can be checked you would do so by removing the outer cover stator cover and using the marks
Click to expand...

That's exactly right. the left engine cover comes off and you should see a line on the rotor. Slip the inductive pick up frum the timing light over the plug wire and fire it up. Point the light at the rotor and see if it moves as the bike revs up. Easy peasy.
 
Teazer that won't work on this bike as the wire and pick up are on the cover and if you pull it it won't fire. The stator has brass pickups in it and the cover has the signal wire mounted to read the pick ups as it spins past. Timing is fixed and the cdi advances as the rpms rise etc.;

Wait no the wire is mounted to the engine so maybe you can run and shine the light on the rotating stator. I have had many beers and my cm has been sold for 2 years or more. Manual will have the info I think. If I can find mine I'll look
 
i dont thunk there is an easy way to observe it.it doesn't have a 2 piece stator cover all the oil will end up on the floor me thinks
 
Thanks for all the great input. I have a PDF copy of the manual and couldn't find anything in it about checking the timing. I'll double check about the stator and see what I can find. Keep the great info coming, and I owe everyone a beer :)
 
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