Certainly its not...but it has to compete with a Laverda and an MV for my affection. At the moment, its a sulky brute!
It would be worth taking the alternator cover off to check the pickups. If you need an oil change, drain it before removing the cover. If not, lean the bike quit a bit to the right against a wall....that will save most oil apart from a tiny spill. Take a photo of each pickup so you note the position of everything and the screw positions. Compare the two airgaps to see if there is an obvious difference. If when you have checked the resistance of them you find one is faulty, buy a pair..... As far as I recall, these are OK..... https://www.electrexworld.co.uk/acatalog/P8.html#SID=403 Also buy some ThreeBond for resealing the alternator cover.
Stripped of alternator cover and measured the air gaps. Both between 1.3 and 1.4mm. Haynes value is .6 to .8. Is the air hap adjustable? Is it possible to measure their resistances whilst still in the bike? Or should I just fit new whatever? I ask out of interest...trying to understand what has gone wrong.
Haynes is just about correct......for once. Workshop manual states 0.027" +/- 0.004"....... that's 0.6858mm
I think so. Renewed the pick ups, plug leads and caps. Got a good spark on both cylinders. Got the engine to run and pull full throttle on the stand. Now need to take it for a test ride.
Further follow up. Continued to fight with poor running and sometimes no running on horizontal cylinder. To cut a long story short, I have now replaced: Coils CDI units Pickups Plugs, caps, leads. The helpful wiring diagram from the Exact people showed that the red and white wires that plugged into the horizontal CDI were the wrong way around. Swapped them and finally got good running on the horizontal cylinder....except its now too good! I had fired it up on the Abba stand. Takes a long time to warm up and accept throttle. Eventually managed to get it to rev to 6k on the choke, backed the choke off and kept the revs at 6k for about 30 seconds to clear things through. Noticed a red glow on the garage floor...the horizontal pipe was glowing cherry red! Shut it down in a hurry. Should it do that? Is it a timing issue or has my valve timing slipped?? Vertical pipe looked fine. I think my fixing enthusiasm has outrun my mechanical talent!
Do you mind posting a summary of where you are with the carburetors? I haven't read all of the thread as it's a bit involved! Putting valve clearances/valve timing to one side, if it's fuelling related the cylinder will be getting hot because it's running way too lean. To assess carburation (aside from balance) make one mark on the twistgrip and mark the throttle housing/switchgear in increments of 1/4, 1/2, 3/4 etc to wide open throttle. Note at which point the engine starts to bog down, in terms of throttle position then post back. Try to avoid running it too hard from cold.
Thanks Travellingman. At the moment I have not been able to get it to tickover which is why I was running the revs up until it was steady on the choke, then backing choke off and seeing if the revs stayed up...which they did but with overheating on the horizontal. Summary with carbs. I reverted to standard jets and needles, cleaned everything up. Put a NOS standard airbox lid and filter on. So I am back to factory settings. The engine is mainly bogging at low revs.
Small throttle openings point you to the idle or 'pilot' circuit. A few questions: - Are the float heights set correctly? - Have you checked the manifold rubbers? Airbox to carb and carb to cylinder head. Ideally by taking them off and properly inspecting for cracks by flexing the rubber. - Have you inspected the diaphragms (same as above)? Air leaks on CV carbs are the first thing to eliminate and will cause all sorts of issues. Taking the plugs out and checking the colour will confirm where you're at. Too lean etc. The other non carburetor cause of severe overheating is an over advanced ignition but it sounds like pretty much everything has been replaced.
Grateful for your clear feedback Travellingman. You and Arquebus are a great help. Will pull the plugs this morning and do a compression test. Depending on that, then a careful check for leaks will follow. At least I have a plan of action...helps soothe the frustration!
Hmm. Both plugs very sooty. No signs of lean running. I guess that makes an air leak less likely? Awaiting delivery of a compression tester.
You're very welcome sir! I'm not sure if I've been much help though. The plug colour is a little unexpected I have to say. Putting the carbs to one side for now, perhaps it's closed up valve clearances, as you previously mentioned. An easy check, prior to the arrival of the compression tester, would be to take the valve inspection covers off and see if you can move the rockers when the engine is at TDC on compression on each cylinder but especially on the horizontal cylinder. Preferably measure the clearances as well but no movement on the rockers would definitely be suspicious. After all the above has been done, then back to the carbs for a final set up.
Methodical, calm and clear advice is always helpful and welcome. Thinking back to when the current problems arose, I was 20 miles into a 50 mile ride when the bike suddenly lost power. It felt like someone had put a sock in an intake. The fact that I had recently treated the tank for rust made me think it was something blocking a carb. But I guess a sudden valve problem would cause similar. I've been chasing geese since then! I'm away from the garage for a couple of weeks now so will update later.
So, update. Compression is equal on both cylinders at 100 psi. I guess check of valve clearances is next step, but of hey had closed up would I get compression? Then I need to check timing I suppose.
An approximate way of calculating cylinder compression value is to multiply atmospheric pressure by compression ratio. Depending on what bike you have here a couple of examples: 750SS - 9.5:1 × 14.7=140 PSI Monster 750 - 9.0:1 × 14.7=132 PSI It may be worth checking a manual, if you have one, as I obtained the CRs from the Motorcycle Specs ZA website and they could possibly be incorrect. The values will vary further depending on the following: - Whether the test was done with a hot or cold engine. - Any variations from the norm in terms of atmospheric pressure, temperature and altitude. The fact that they're the same is a good start though.. As you've intimated, it's just a process of eliminating potential causes.
just checked my haynes manual cylinder compression as standard should be 130 to 160 psi minimum should be 116 psi with a maximum of 29 psi difference between cylinders if thats any help doesnt state if hot or cold when readings taken also i seem to remember being told when doing compression tests to hold carbs fully open for it to allow air in rather than with carbs closed .......not sure if thats correct ........sure somebody will clarify it on here
I'd agree, always understood that readings around 120-140psi indicated good compression and anything much below 110psi indicated something worn or amiss.
Apologies for the rather sporadic posting but my opportunities for getting into The Shed have been limited of late! To recap, I was chasing a poor running situation with severe lack of power and inability to run at low throttle settings. I has previously rebuilt the carbs and put everything back to standard. Plug check showed sooty plugs with no sign of lean-ness. A lack of running on the horizontal seemed to have been cured by renewing the entire ignition chain from the pickups to the coils and plugs. But then horizontal cylinder severely overheated. Compression test from stone cold, wide open throttle gave 100 psi on both. I have now checked horizontal cylinder valve clearances and they are in spec. (0.10/0.02 mm inlet, 0.15/0.05 mm exhaust). The drive belts and cams are correctly set up. So only my compression is out of spec but its equal for both. I have either messed up the carb rebuild (but horizontal plug was not showing leanness) or I have a timing issue?. I'm reaching the point where I might have to ship it off to an expert I think.
