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Discussion Starter · #1 ·
Dear all, I am new here on the forum, so first let me thank to everybody who keeps such a nice Honda comunity up and running. It´s great that one can read what other is proud of.

I am proud owner of my first Honda, CM400 custom, just recently bought it from Germany and import it into Czech republic, which is my home land. I already have oldtimer, Yamaha XS400 4G5 in cafe racer modification. My plan with honda is to keep it in original look, but restore and make it brand new.

Before I start, I wanted to make sure that everything is running. And that´s the moment when my story begins. Seller told me that she is working and running, however I bought it remotely and when I recieve her, there was head cover just sitting there, carbs were very dirty and on top of that, there was extra camshaft included with bike. That´s actualy makes me wonder what pre owner did with the bike.

Anyway, I cleaned carbs, I think properly, by industry ultrasonic cleaner I have at home, assembly it back, set vlave clearence and try to fire her up. Unfortunatelly, she won´t, engine turns with no any strange noise or anything, plugs give sparks and electric seems to work. Time to time, she behaves to fires up, but only what it does is sort of flame to air box/back fire.

Have no idea how long she was not running, but according to carbs condition (were sticky inside from vapourised petrol) I guess about 10-15 years.

I would like to kindly ask you for your help, opinions what to check or any ideas what could be an issue.

I also ordered rebuilt kit for carb, becuase there is gasoline leakage, somewhere around connection pipe between two carbs. Carbs has plastic floats which actually doesn´t allow you to adjust float height, interesting.


Thank you very much in advance for all your ideas and tips. Hope my english is understandable for you, guys, since I am not native speaker.
 

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Have you tried adding a bit of gas or starter fluid to the carbs? More experienced guys may have further help.
 

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Discussion Starter · #3 ·
Have you tried adding a bit of gas or starter fluid to the carbs? More experienced guys may have further help.
Thank you. I haven´t try that, but I should, so I will.

Actually reading thru forum and wondering if timing could be 180° OFF and how. Somebody exchanged camshaft and put it all back wrong?


Thank you.
 

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Here's some good information to help get you started"

http://www.hondatwins.net/forums/67...n/16105-basic-checklist-new-you-old-bike.html

Your bike uses a wasted spark ignition (both plugs fire every revolution) so ignition being 180 out wouldn't matter. About the only way ignition timing gets off is if the key that holds the flywheel shears. The camshaft could be out of time with the crankshaft and, considering what came with it, that would be worth checking.

Among the multitude of great information in the SOHC section of the forum you might also take a look at this one when you get ready to tackle the carbs:

http://www.hondatwins.net/forums/63-fuel-supply-carburation/24191-rebuilding-vbulletin-carbs.html

PM sent about manual.

Welcome to the group.

Got pictures?:p
 

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Discussion Starter · #5 ·
J-T, thank you very much for your reply and also for PM, I really appreciatte it.
I will do next steps in upcoming days.
 

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You mentioned that you cleaned the carbs, did you make sure to set the pilot screw correctly?

Also, please be careful with starter fluid. One very small, very short spray is more than enough :D
 

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Discussion Starter · #7 ·
Yes, I set pilot screw according to manual, which says 1,5 turn out. In any case, fromy my yamaha experience with different, but still CV carbs, it doesn not really matter for start up.
However, just came to my mind assembly of pilot screw....does it have only screw, spring and washer or am I missing o-ring?
 

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You have manual now, yes ?

You know of cmsnl for the exploded views which can only help you !!

Pilot screw, the brass screw under the carbs, see manual and exploded views.

Yes they do have an O ring.

When assembling, screw held with head below, fit spring, washer then O ring, then fit to carb.

Sometimes when removing the screw from the carb, the little o ring can get left in the hole, and if not known about, can be damaged when refitting the screw, even to the extent that the o ring gets "mangled" and "pushed into" the very small "air/fuel" passage, so be very careful !!
 

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Plastic floats, good, but they use different float needle valves that are designed for these floats, see cmsnl for differences, or Davidsilverspares, or similar.

Bike been standing for 10 to 15 years, with cam lid off ??

I hope you checked that the valves are free and opened and closed all ok ?

Check timing with manual, but see timing marks. From memory the Yamaha pistons are out of phase ( one rises whilst the other falls ) but the Honda, the pistons are in phase, ie rise and fall together. Look for "T" and "F" on flywheel, a standard Honda marking, and the 2 lines on the camshaft cam chain sprocket, which on "T" will be level and parallel ( in line with ) with the cam cover cyl head sealing face.

Any "Lean back" of these lines at "T".

You know how to adjust the cam chain tension via the manual, and valve working clearance.

I would also check the balance chain adjustment, via the slotted cover on the clutch cover. Research this system, you have the manual and exploded views.

You will be able to see the "DOT" thru the slotted cover window, and, will be just able to see the actual balance chain, but its an bit of a "knack".:roll:

A long thin probe can be inserted and chain slack "felt", but only with the engine NOT RUNNING.

Warning about ht, either use red neon plug caps for easy visual ht inspection, very useful diagnostic aid and relatively inexpensive, or, make ht tester. The cdi system will not like a poor earth. Remember that the cam cover, when fitted, is insulated from the engine by the rubber gasket and rubber washers, so is not a good earth !

Metal strip, either weld or screw 2 old working plugs to strip, make a flying earth lead with crocodile clip.

With valves all good, what is the compression like, more or less equal between cylinders ?

Post some pictures of the cam and valves and cyl head bolts as well as the front of the engine between the cylinders.

If you have had the Yamaha engine apart ( you know of the cam shaft "sweet spot" then ) you will not realy have a problem with the Honda, once you know about the "Honda way" and its "oddities".

Study cmsnl engine exploded views, print them off if you can, then study the manual, but most of all, take your time and enjoy.
 

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PS drain engine oil and inspect, also oil filter and filter cover floor, but find "washer"., I assume you have a small engine run test tank so fuel is clean, also use in line fuel filter.
 

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Discussion Starter · #11 ·
Interesting investigation today. As mentioned before, I got extra camshaft with a bike, have no clue why since that's not a cheapest thing, however, I found that somebody put timing chain wrong by few teeth according to timing marks on camshaft. So I adjust it, set clearance again. Still she doesnt want to come to life, unfortunatelly. Still thinking...you know, in europe, there was reduced power to 20kw while in Usa was 35 I think. Only difference was in camshaft or something else? What If preowner wanted to in rease power and tried to use differe t camshaft.

Thank you for ideas.
 

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Being a German model there were 2 camshafts available, normal and reduced power. I have no idea about markings to determine which is which. I'd say chose the one with the most lift as the most likely "normal" cam
 

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Discussion Starter · #13 ·
thank you for all advices.
Guys, still nothing, now I don´t know what to do next. One thing, I am trying to start up with not airbox connected, do you think it is big issue? I guess she should atleast comes to life.
When I found few teeth timing chain off, do you think it could cause anything? Because I fixed it but still nothing.

Thank you.
 

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If the timing chain was only a few links off I doubt the valves would have contacted the pistons. If they had the valves could have been bent and would stick partially open.

Missing air box would be an issue if you tried to ride it, but it should start and idle OK.

After you try to start it, are the plugs wet of dry?
 

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Discussion Starter · #16 ·
Plugs are wet. I just ordered compression tester, so still I am not able to measure it.

I took carbs again and trying to cleam them. Seems to me that carbs doen´s work as they should. If I have carbs out and put hand on the cylinder intake, engine creates great vacuum and seems it suck strong, but when I have carbs on and uses choke, carbs are spitting fuel to airbox direction, literally spitting. Then it leakes on the top of carbs, where vacuum pistons are. That actually guides me to ask about orientation of plastic sealing there. Service book says one direction while CMSNL says other way round.
 

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The white plastic rings under the vac pistons, lip up from memory but should be obvious which way round they go ?

Spitting fuel or flames/vapour as well, and seem to want to stop dead ?

Flywheel "T" aligns with upper crank case reference mark at TDC , yes ?
 

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Discussion Starter · #18 ·
Yes, flywheet T mark allign with TDC, then I have 0.15 mm exhaust and 0.10mm intake clearance one side, then I turn flywheel one turn, again to T mark and do other cylinder. Starting from left one.

Yes, spitting fuel back and doesn't want to start. Few time I got flame or tendency to start but only tendency.
 

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Using a straw thru one plug hole rotate the engine to find TDC, where the straw rises and then starts to drop again. Fiddle back and forth until it's as close as you can get. Now check that the rotor T mark is aligned with the pointer on the case. It's been known that the woodruff key can shear off and allow the rotor to move out of time.
 

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Discussion Starter · #20 · (Edited)
Hi friends, I am here with update....No compression at all. So now I am about to disassemble head and cylinder to check out what is going on inside.
Anyway, if I am there, I would like to exchange pistons and rings. Do you, guys, have any tips where to buy piston kit for reasonable price and more important which ones.
I don´t really know which ones are right, since bike documentation says 1984, but I think it is 1981, type C. However, can anyone is able to identify from bike code (NC013201900). Or is there any other pistons, which fits? I think I will got 2nd oversize, for sure.

Thank you very much for help.
 
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