Leak down test

[philmill]

Hi guys, I have dragged the Hybrid out of the corner with some fresh enthusiasm, I need to get to the bottom of the hard starting (non starting now). As some of you may remember I posted some pictures of oil leaking from one of the crankshaft dowel pins on the lower crankcase, I assumed that I had an air leak from here. I have now done leak down test and it all seems to be good, no obvious signs of air leaks. Just to put my mind at rest, what pressure do you suggest putting in and how long should it hold? I put 5psi and thats been holding now for well over 5 mins with less than 1psi drop. I have sprayed all the joints I can get to and all good, the clutch case is one though so I cant get to that seal.

Just to go back over the history, when I rebuilt the bike and first started it around 4 years ago it started 2nd kick then during the heat cycle process always started 1st or second kick, but after a few months it became harder and harder to start. I have now got the carbs off so will give them a fresh clean but its a bit strange. 

I would like to get this sorted so that maybe i'll actually ride it soon, its been a long project with its fair share of issues, but she looks great and needs to be ridden.

Phil

IMG_0051 by Philip Millard, on Flickr

[abar121]

I just pressure tested my RD400, also did 5 mins at 5psi without dropping. I'm happy with that

Looking on here it seems that YPVS seals and also reeds are common places for leaks. Not had that myself as yet.

Love the hybrid. My suspicion would be the carbs or fuel flow. I use clear karting fuel lines from the tap. They don't harden and you can see the flow.

Could also fit a new pit bike (banshee coil), also check that you're running either resistor plugs or boots. Then it's down to checking the stator, connections, CDI if an early 31k etc.

[johnrd350lc]

Aug 18, 2022 15:43:17 GMT 1 philmill said:

Hi guys, I have dragged the Hybrid out of the corner with some fresh enthusiasm, I need to get to the bottom of the hard starting (non starting now). As some of you may remember I posted some pictures of oil leaking from one of the crankshaft dowel pins on the lower crankcase, I assumed that I had an air leak from here. I have now done leak down test and it all seems to be good, no obvious signs of air leaks. Just to put my mind at rest, what pressure do you suggest putting in and how long should it hold? I put 5psi and thats been holding now for well over 5 mins with less than 1psi drop. I have sprayed all the joints I can get to and all good, the clutch case is one though so I cant get to that seal.

Just to go back over the history, when I rebuilt the bike and first started it around 4 years ago it started 2nd kick then during the heat cycle process always started 1st or second kick, but after a few months it became harder and harder to start. I have now got the carbs off so will give them a fresh clean but its a bit strange. 

I would like to get this sorted so that maybe i'll actually ride it soon, its been a long project with its fair share of issues, but she looks great and needs to be ridden.

Phil

IMG_0051 by Philip Millard, on Flickr

[johnrd350lc]

Nice bike I hope mine looks as good.

[midlifecrisisrd]

Are you using the original 29k50 cdi?

Steve

[philmill]

Aug 18, 2022 17:33:32 GMT 1 midlifecrisisrd said:

Are you using the original 29k50 cdi?

Steve

Hi Steve, yes, do you think it could be that then?? is there a way to test it??

Phil

[philmill]

Aug 18, 2022 16:12:27 GMT 1 abar121 said:

I just pressure tested my RD400, also did 5 mins at 5psi without dropping. I'm happy with that

Looking on here it seems that YPVS seals and also reeds are common places for leaks. Not had that myself as yet.

Love the hybrid. My suspicion would be the carbs or fuel flow. I use clear karting fuel lines from the tap. They don't harden and you can see the flow.

Could also fit a new pit bike (banshee coil), also check that you're running either resistor plugs or boots. Then it's down to checking the stator, connections, CDI if an early 31k etc.

I am using the upgraded coils, but I guess electrical is something I hadn't considered, I do have a decent spark.

Phil

[steeley]

A mate of mine is chasing an electrical fault on his Yamagamma . 31k electrics , i have lent him a coil / cdi from my own Yamagamma to see if he can get to the bottom of it . I said the cdi on them get flaky with age .

[midlifecrisisrd]

Normally they either don't work or work for a period of time then stop but I did have one that would only misfire or backfire so possible to give the wring timing

Speaking of wrong timing check the rotor nut hasn't loosened or pick up is loose

If it started before but not now something has changed

Also check fuel flows out the tap. I had a paint job that the painter hadn't cleaned after it had been dip stripped. Tank was full off old crud that clogged the filter

Also check debris haven't blocked the pilot jets

Steve

[midlifecrisisrd]

Also meter out the lo speed windings on the stator. If ropey they may not make enough power when kick starting

Steve

[muttsnuts]

I'd say CDI is faulty

But I'd be checking the following (whether new or not)

1. Coil
2. Stator windings
3. Pickup
4. CDI (quick swap out)
5. Compression test
6. Carbs sound like they have been done to death - just double check the choke bowl is on the LHS carb and that the pipe between the 2 carbs is snug and in good condition
7. Vacuum pipe from RHS carb - check for air leaks/splits etc
8. Run it up on an Aux petrol tank to rule out the fuel tap/fuel tank etc (be sure to blank off the vacuum hose open end)
9. Spark plugs - fit new ones (just in case original ones have fouled up during heat cycling)
10. Engine/bike earths
11. Kill switch - pull the kill switch wire out of the loom (red/white or black/white depending upon loom used)
12. Ignition switch (disconnect it, loop permanent live to switched live), this removes the "kill circuit" on the ignition switch - I've seen this issue several times

Do in any order you choose, but just my tuppence worth

HTH

[philmill]

I thought I'd continue on this post.... so the bike is running, I stripped the carbs, put fresh fuel and plugs and it started 2nd kick, so well chuffed. Funny how things go, having had the bike nearly finished 3 years ago all the little niggly issues meant I'd put it in the naughty corner and left it alone, however, after the renewed enthusiasm and the joy of it starting meant I've got on and sorted most of the issues, and today I rode it up my driveway a few times. She seems to run well, and sounds awesome, a trip to Muttsnuts will have to be booked I think after he'd had the porting etc done i think it should be set up properly before being used in anger. Next stage is MOT.

I still have 2 niggles, one I only found today, that is the the swinging arm hits the banjo bolt of the rear brake master cylinder, I'm guessing I've done something wrong as the VJ swinging arm isn't something new on a 31K, so input please, what am I missing? the arm doesn't lightly touch, it hits the banjo bolt and stops there. Master Cylinder is Brembo. Other issue is the bloody electronic tacho, this is one of the long running things, not going to stop the MOT but I would like to sort it. I have bought 2 tachos now and neither work,( I assume no way to test a the unit off the bike?) I have tried the wire on different leads on the Power Valve servo but nothing, can anybody show me a pic of which wire from the original loom I should be connecting too.

Thanks,
Phil

[beardy]

Just of the top of my head. Does the footrest hanger need to be spaced out from the frame? I don’t own a hybrid or pv so just guessing 👍🏻

[beardy]

Or even the master cylinder having looked at the pics

[jessy03]

I used some spacers 👍

[midlifecrisisrd]

As said you need to space off the master cylinder to get it to clear the arm

As for the tacho if it's a normal f2/n2 tacho it will need the trigger connected to the black/yellow wire at the cdi or pv controller

If it's a later RZ tacho some are that but the last ones need triggered from the orange coil wire

Good you've got it running 👍

Steve

[abar121]

Aug 20, 2022 17:50:55 GMT 1 jessy03 said:

I used some spacers 👍

I love those indicators, what are they?

[jessy03]

Just some cheapo ones off eBay 👍

[midlifecrisisrd]

Aug 20, 2022 21:36:43 GMT 1 jessy03 said:

Just some cheapo ones off eBay 👍

Just something like these in whatever size You need

www.ebay.co.uk/itm/193391036716

Steve