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Peter Sheppard
New member
Username: puffernutter
Post Number: 3
Registered: 10-2005
| | Posted on Thursday, November 24, 2005 - 07:20 pm: | 
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I now have my P5 to play with! I have read various threads in this forum on the P5 particularly about starting. This engine has not been started for a number of years. It has a centrifugal clutch and impulse magneto (P5MC?) There is a spark (I think it comes at the right point, I set it according to the manual). There is fuel, maybe too much fuel and that could be the problem! I have checked the jet and it is clear, I have taken the float out and cleaned all the debris out of the float chamber, however whilst it appears to seal, I still get drips of petrol out of the carb, so I suspect that it is not sealing as well as it might? Could that lead to a too rich mixture and the reason why it is not starting. If so, what can be done to clean the seat. A (silly?) question what position should the throttle be in for starting? Is the plunger in or out of the carb? Finally, just to clarify, am I correct in thinking that the P5MC does not have a starting cam?
Thanks in anticipation
Peter |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 270
Registered: 09-2002
| | Posted on Wednesday, November 30, 2005 - 06:22 pm: |
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Peter.......firstly ,yes there is a starting cam on the P5. It will open the throttle just a bit ,plunger comes out to open . Sounds like your float valve is leaking . You can easly check this by unsrewing the top of the float bowl. You can then see the fuel level . This is pre determined by the valve spindle ,it has a groove that locates the float in a fixed position. So if all is well ,ie the float does not have a small leak and this can happen . Check by immersing in warm water and watch for bubbles. If the float valve leaks then lap it in with some ''Brasso''. If both of these points are ok the fuel level will be correct.
Check the fuel/air mix.....these is adjusted by screwing the brass perforated air intake in or out . Out is more air , a good point to start from is that it is unsrewed about a 1/4 inch out.
I am about to make some new piston rings for my P5 ...these engines love good compression.
If you wish i can send a pic of the starting cam arrangement. |
Peter Sheppard
Member
Username: puffernutter
Post Number: 4
Registered: 10-2005
| | Posted on Thursday, December 01, 2005 - 08:30 am: |
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Peter,
Thank you for taking the time to give me some pointers.
Prior to your post I had investigated some items. Knowing that the minimum requirements were petrol, air and a source of ignition I worked my way through the relevant parts of the engine.
I have removed and stripped the carb. I don't think that the float needle was seating properly. I tried brasso, which didn't have much effect, I then used a small end-mill to lightly reform the seat. That seems OK. The float also was OK and I made sure that it sat in the groove on the needle.
It is surprising how much "assumed" knowledge the user manuals. I hadn't appreciated the purpose of the air intake. Mine is screwed all the way in (well it was anyway, it is now out by 1/4"!).
I have checked the carb needle and that also seems OK.
I then removed the magneto (it is an impulse type on this engine). This also means that I don't have a starting cam -I have to depress the float needle to get fuel in the carb/engine. This may be what has led to fuel coming out of a hole in the bottom of the carb body.
I adjusted the drive as per the manual, checked the plug gap and the points gap. There is now a clean blue spark (hopefully at the right point).
Two nights ago it ran briefly without being able to pick up speed (it just died). Last night it wouldn't start! Petrol engines, who'd have 'em!
Tonight I will re-check the magneto setting, adjust the air intake and see what happens.
One last question, with the impulse magneto, the trigger doesn't seem to operate every time when turned by hand. Is this usual? I was wondering if when it was running there was more rotational force (centrifugal) which meant it would work every time. It was just that hand-cranking was too slow.
Cheers
Peter |
Andrew Menkart
Moderator
Username: andrew
Post Number: 1258
Registered: 11-2001
| | Posted on Thursday, December 01, 2005 - 09:41 am: |
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From Peter O. by email:
quote:Peter ,
you are correct re the impulse magneto and centrifugal force. If your engine just dies and wont get away ....a couple of things .
Is the fuel getting through from the tank OK ,ie check the small breather hole in the tank cap. You would be surprised how often this is the problem.
The other point is the muffler and exhaust system . If your engine has done a lot of running hours and the owner has been over generous with the oil mix the whole system may be coked up.
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Peter Sheppard
Member
Username: puffernutter
Post Number: 5
Registered: 10-2005
| | Posted on Thursday, December 01, 2005 - 10:48 am: |
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Andrew, thanks you.
I am happy that the fuel side of things is OK now (petrol delivery at least!) All parts have been totally stripped and cleaned. If I depress the float needle I get a good spurt of petrol through the float chamber cover.
How do I clean the muffler and exhaust system? Remove it (obviously) then wash it through with petrol, attack it with a scraper, give it a good bang on the work bench, or all three! :-) |
Peter Ogborne
Senior Member
Username: peterogborne
Post Number: 272
Registered: 09-2002
| | Posted on Sunday, December 04, 2005 - 05:48 pm: |
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Peter....I thought I had posted something about cleaning the exhaust system...so here goes again.
Take off the cover plate on the expansion chamber. The condition inside will give an indication as to the rest of the system . If you start scraping out the carbon make sure you block off the ports [a bit of rag].
To clean the muffler and pipes a hot caustic bath is the best way . If you do it yourself be very careful ,best if you can find a business that has a bath, It is dangerous stuff. |
Peter Sheppard
Member
Username: puffernutter
Post Number: 6
Registered: 10-2005
| | Posted on Monday, December 05, 2005 - 07:09 am: |
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Peter, Andrew
Thank you. But it still won't start again!
This is where I am up to -
The spark is good and at the right time, so I reckon that the electrical side of it (impulse magneto, cable plug, points gaps etc. is all OK)
Compression is OK? I have measured 65psi in the cylinder on a hand cranking. Possibly a little low, but then I only know 4 strokes!
Expansion chamber - full of thick oil. Now cleaned out. Ports look OK. New gasket and re-sealed
Fuel - this is where I suspect the problem still is. The float valve "appears" to seal, yet I still get a constant outflow of petrol from a hole in the very bottom of the carb. The float seems OK (I will check it again) but when I unscrew the cap off the float chamber, the petrol seems rather high (above the hole that leads into the carb) so is that the problem? The float is sitting correctly on the float needle and the float chamber is vertical. Is it possible that the needle is not quite seating and whilst there is no noticable increase in level, it is just enough to continuously trickle into the carb (making it overrich?)
Oh, and by the way, since it was running last week, I haven't been able to start it again!
Help! (Sorry that this is a long post!)
Cheers
Peter |
S A M
Visitor
| | Posted on Monday, December 05, 2005 - 08:29 am: |
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There's nothing like trying to start a flooded two-stroke! Give it a good bit of whirling with the fuel off and plug out. Also, I don't specifically know about the P5, but most S-T's have a crankcase drain plug. If you can find one open it up and do a bit more twirling to clear the engine of accumulated stale petroil mixture.
If all else fails try a puff of gypsy's breath (easy start). |
A.Nicholas Cowan
New member
Username: nicksearcher
Post Number: 2
Registered: 06-2006
| | Posted on Friday, July 14, 2006 - 10:26 am: |
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Thanks for the suggestion, Peter O. Yes, the magneto is the A type with the bakelite cover. There was clearly some slipping of the key on the taper, so I tried 'Screwfix'compound, but the 'click' impulse still reset itself, and the engine refused to start. I assume the correct position for the lugs on the magneto is right up against the hard resistance when the flywheel is at 2in.before TDC? Immediately clockwise after the hard resistance is felt, the click (and spark) occurs. |
A.Nicholas Cowan
New member
Username: nicksearcher
Post Number: 3
Registered: 06-2006
| | Posted on Saturday, July 15, 2006 - 08:50 am: |
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Sorry, I posted this reply in the wrong discussion section. Regarding flooding of carb.and crankcase, find the brass nut right at the base of the port side of engine, next to engine mounting bolt. Partly, or completely unscrew, and oil gunge can leak out. Re-tighten. See other postings for advice on reseating carb. shut-off needle which is attached to the float. Any dirt can also cause flooding, i.e. needle fails to close off petroil. |
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