BBK non started troublshooting

[slawenm]

Well story is BBk installed, and the bike wont start.

The bike is getting a spark from the plug when its against the frame.

all wires cables and pipes are all reconnected into the same place they came from I colour coded it all as I took it apart.

fuel is getting to the carb as I turned the drain screw on bowl and it had fresh fuel in there

has fresh oil a brand new exhaust

two things I've noticed one the kick start is very easy to kick down, mean lack of compression? if so how... everything is tightened up right with gaskets etc

next thing I can think of is I had valve swapping trouble with my head so I admitted defeat and went and got a head from else where, could they be longer valves when I put the rocker arm back on it was already compressing the valve springs just hand tightened on to set the valve to the right gap I had to undone them quite a lot.

Do I honestly need to head out and buy a third head with the shorter valves my stockhead had and my rockerarm is meant for....

[Fox]

You should be able to feel the compression when you work the kick lever. Make sure that the cam is aligned properly when the T mark is aligned and that the valves gaps are right. The worst thing you can do is rush the job. Make sure everything is right before you try to start it cause if you bend a valve than you'll be buying a new head.

[slawenm]

cam is aligent and is on the T with the I gapped to 0.05mm which is the size gaps I've always used on this scooter

just measured my old valves and they are 64mm or there abouts now to adjust the valves on this brand new head I had to move them out a few mm because they we're already compressing the springs. so I think maybe this new head came with 69mm valves and my rocker is meant for 64mm, this time I am buying the damn compressor

found one on ebay www.ebay.co.uk/itm/NEW-Valve-spring-compressor-suitable-many-Honda-engines-Valve-spring-compressor-/390358455523?pt=UK_Motorcycle_Parts&hash=item5ae32d54e3#ht_1202wt_1031 its close enough to the type Brent has linked me on another thread. going to restrip the bike when I get a day off work.

Didn't even know valves come in two sizes until I started searching around the forum just now

[slawenm]

bollocks realised what I done now, I've set to 0.05mm instead of 0.12mm

are over tight valves likely to cause non start or even any damage trying to tick over with tight valves?

[Fox]

.05mm is correct. Take the valve cover off, loosen both valve adjusters till they are really sloppy, re-torque the 4 main head bolts and then reset the gaps. It's better to have loose valves than too tight.

[slawenm]

sounds like a plan my confusion come from I used to use an inches feeler gaguge and gap to 0.004" but now I have an mm one and I put to 0.05mm

convesion I did from 0.005" to mm is about 0.12m

thanks for all your help guess I rushed a ittle tired of using public transport to get to work wanted to go under my own steam tomorrow

[Fox]

.05mm=.0197 in. I do mine to .003 in. That extra thousandth of an inch isn't enough to matter. Truth is anywhere from .002 in. to.004 in. is within tolerance and the engine will run. If you can hear them tapping loudly at idle then one or both is set too big.

[slawenm]

yeah maybe the gap wont be the problem, when I get time I'm going to take rockerarms and cam etc back out and reinstall them all again see if I went wrong somewhere, and see if theres any or much damage... got a spare valve less head and a pair of valves I cant install without the tool spare so I can buy the tool and make use of both of them.

just going to keep throwing money at this thing until it bloody works. I need my own transport for work.....

[Fox]

Good for you! Take your time! Stare at it for as long as it takes til you fully "get it"

[slawenm]

took the rocker cover off with the last bit of daylight. have markings on two of the post for the rockerarm E X which when installing I figured was for the exhaust so thats how its fitted would this be correct?

no daylight now so I'm leaving be till weekend. just want to make sure I put the rockerarm on right.

[90GTVert]

That should be correct.

[slawenm]

blah so everything is almost sorted seems my inlet valve got bent and stuck open.

my question is... 360 degree turn of my flywheel is 180 degree of my cam and both TDC are at top of the piston how can I tell which is compression stroke and should my exhaust valve be the first one to open after the compression stroke?

really dont want to put this thing back together and bend another valve or worse next time

The cam has been off for awhile now so I cannot use its holes as a guide cant remember if they was showing or not when I took the cam out the first time.

[Fox]

Intake valve opens and closes, then compression stroke, ignition, exhaust valve opens and closes.

All you have to do is line up the T mark on the flywheel. I usually duct tape the damn thing so it doesn't move off the T mark, then install the cam with the holes lined up as shown in the valve adjust guide. That's it! Done! There is a wasted spark on these so it doesn't matter electronically.

Valve adjust:
49ccscoot.proboards.com/index.cgi?board=4ttech&action=display&thread=428

[slawenm]

everything engine wise done today, everything was lined up valves set put engine back it and she still wont start but got close to it afew times.

after a short while it sounds like my starter or bendix gear is jamming.

could my battery or starter not have the power to crank over the large bore bike?

I put in an unlimited CDI and hotter coil just to try help with starting and no change.

[Fox]

If the battery gets weak then it won't spin the starter fast enough to extend the bendix spring so it'll grind or you'll just hear a whirring sound. You can hook the scooter battery to a car battery with jumper cables so you don't flatten your battery. No need to start the car engine. Just hook them up. BBK's sometimes do have too much compression for the starter. You can lower the compression by adding a second base gasket under the cylinder.

One other thing is you don't want to crank the starter for extended periods because it can overheat the starter motor and damage it. Let it cool off for a while after cranking for 2 or 3 minutes.