SOHC.co.uk Forums > CB500/550

It won't start!

<< < (2/4) > >>

SteveD CB500K0:
I've heard of a few 750s with blank crankcases.

If they were replaced due to damage (usually when the drive chain let go on the 750), the dealer/mechanic should have hand stamped the engine number onto the replacement cases.

It obviously didn't happen.

florence:
If you take a length of brass wire (long enough so you can't drop it completely down the plug hole) you should be able to put it down the plug hole and as you turn the engine over gently on a spanner you can feel which direction the piston is moving.  Take off the rocker caps and watch that the inlet valve is opening as the piston goes down rather than when it is coming up.  The valve timing may look right but in fact could be 180 degrees out.  If someone has assembled it incorrectly a top end strip will sort it out.

As for the blank cases, a friend of mine bought cb350 crankcases new from david silver spares as his original ones were damaged.  The new part came without a number on it.

matthewmosse:
Good idea, I'll give it a shot as this could explain things, Also it occors that camshaft or rockers will be a much easyer prospect to replace, I've just got a set off ebay recently, just a bit of a pain as I only got this engine to avoid spending the time cleaning up enough and then rebuildig an engine as the workshop is currently a building site as well. Such is life, I'm lucky to have a workshop at all really. Oh well, geuss I'd better set to and do, sometime or other..........
Cheers for now.
Matt

Bryanj:
If you or somebody previous didnt use the trained spider to hold up the rockers when fitting the top cover some valves may be bent
Also cam 180 out dont matter a stuff as 1&4 rise together and spark together (as do 2&3)
What is the actual compression reading as less than 140 will make for hard starting on an engine thats been stood
how long have the carbs been stood
apart from oil peeing out there is no reason you cant do a compression check with the rocker cover off--as long as the cam is in with chain connected

matthewmosse:
Hi, I checked compression with rocker cover on and off. I always check the oilways this way on an unknown/ rebuilt engine as the first one I rebuilt had a dodgy o ring that was too big and defrormed when cranked up and closed up the oilway, result a dropped valve, knackerd jornal bearing and camshaft, holed piston and bust con rod and a hole in the cases. all from a cheapo pattern gaskett set with dodgy sized o rings. Moral of the story:- always have a genuine set to compare against and always check oil circulation before touring Scotland and back! I agree on the cam timing comment, I'm thinking maybe someone installed a funny proflied cam. I actually tried spraying easy start up the exhaust and for the first time It tried to run! then I decided to install a new bathroom and tidy the shed! I found an engine that only needs the kickstart sorting! by the way Haynes tell us we need to split the cases to sort the kickstart mechanism. Not true! The kickstarter can be replaced with sump off and cluch cover removed. I tried and succceded! I've found a few bloomers like this in the manuals ::) the actual reading is a bit duff on compression tester, if I believed the numbers my tester read none of my engines would ever have run but they compare well with known good motor, as in started if I breathed on the button, shame the gearbox and primary chain were worn out. When the bathroom is done I geuss the bike will get a look in ;)

Navigation

[0] Message Index

[#] Next page

[*] Previous page