Top end of first gear haemorrhages?

[Staticam]

The Cagiva has been sitting for a while so I decided to take it out for a wee pootle last weekend. It started third crank, off I go. Took a nosey around a new nearby subdivision, enough of that. On the way home I gave it the beans but it went to pot, what the! So tried again, same result, it just boggs out. Backing of its ok, changing up its ok. I think it'll bog at the top of second too but that's a bit quick for the urban enviro. I didn't take it out on the open road. Just went home and shoved it back in the garage.

So...
First gear no real load, it wont go past three quarter rev range. I have no tacho but it normally happily revs higher.
It is very clattery, probably loose exhaust valve clearance. Could this be the problem?
I know what electrical HT brake-down feels like in a car, this doesn't feel like that.

I plan to tackle setting the valves then take it for a better road test.
Before I do that - does anyone here know what the problem might be?

Cheers for any ideas.

[imdying]

Change the gas.

[Staticam]

Change the gas.

Can do, but wouldn't old fuel fail cause issues under load and initial throttle?

[Staticam]

I tightened the exhaust valves (they were loose, probably could still go a bit tighter) and changed the gas. It's still got a problem. 1st, 2nd and 3rd gears wont pull at the top of their rev range, it just bogs out. Despite my earlier comment, maybe it is electrical. I changed the spark plug, no improvement. Is there a way to test the CDI unit ... or what else to do?

[Kickaha]

The Cagiva has been sitting for a while

How long is "a while" you may need to strip and clean the carbs

[Staticam]

How long is "a while" you may need to strip and clean the carbs

carbs! I wish but it's just a single banger :(
In this case a while means I haven't been riding it frequently, once every couple of months for the last six. The bogging out, spluttering, missing, whatever - stops as soon as the throttle is let off. Grab the the next gear and its ok, it just chugs away with all its massive torques :wait:

[bsasuper]

I've had bikes sit for 8 months, and they started fine with the old fuel, were fine around town, but just as you describe no top end.

[vifferman]

Realistically, the only thing that's changed while it was sitting around is the fuel, unless some rubber component has been gradually degrading and eventualy ended up at the point where it's kaput. My bet would be there's some varnishing of the carb components from fuel evaporation, and/or some buildup of moisture. Try draining the carb, and buy some carb cleaner or fuel system treatment (don't use too much on the basis that "more is better" as it will soot up your plug.)

[Staticam]

I've had bikes sit for 8 months, and they started fine with the old fuel, were fine around town, but just as you describe no top end.

and ... did they come right?

[Staticam]

Realistically, the only thing that's changed while it was sitting around is the fuel, unless some rubber component has been gradually degrading and eventualy ended up at the point where it's kaput. My bet would be there's some varnishing of the carb components from fuel evaporation, and/or some buildup of moisture. Try draining the carb, and buy some carb cleaner or fuel system treatment (don't use too much on the basis that "more is better" as it will soot up your plug.)

I completely emptied the gas tank and put new fuel in. This thing just idling for two minutes would probably empty the carb so I reckon clean fuel is running through. However, giving it a strip and clean it is quite doable, I'll give that a go.

Hmmm yes rubber components - one of the fork seals has gone, though not from sitting. And the valve(s) for the rear brake master have failed :pinch:

[paturoa]

When you changed the gas did you drain the float bowl? Water will sit in the bottom of the bowl. I'd also recommend a half a cup of meths in the tank too.

If it starts and runs OK at smaller throttle then the pilot jet is prolly OK so don't fark with that.

[Staticam]

I had another go at the bike today. Fired it up (very clattery), got it warm (still making a racket) and found that even while in neutral it will not pull high revs. I took the carb off. It’s clean and the diaphragm looks fine. I put it back together, restarted, same results.

This is where I’m at:
-Fuel and carb are clean.
-The spark plug I tried previously was used and the wrong temp but I figure has 95% ruled out a faulty plug issue.
-Clattery noise, sounds like valve clearance but could also be chain tensioner or something else?
-Wiring - the side cover has been off and on recently to sort out the starter clutch. It’s a real mangle getting the alternator wiring past the oil pipe.

It's such a waste just sitting there, what to do next?

I'm trying to sort it out without going to the shop, although I'll take on board any good recommendations.

[breakaway]

What is the state of the battery? How many volts does it show when you put a multimeter acrossit? Is there an in-line fuel filter? Have you checked the fuel line for blockages / kinks?

[Staticam]

What is the state of the battery? How many volts does it show when you put a multimeter acrossit? Is there an in-line fuel filter? Have you checked the fuel line for blockages / kinks?

Thanks for the ideas. The battery is one year old and has been on a tender which says it is ok. No in-line filter, lines are smooth, carb filled and engine started on first crank after having had it all appart.

[BoristheBiter]

I had another go at the bike today. Fired it up (very clattery), got it warm (still making a racket) and found that even while in neutral it will not pull high revs. I took the carb off. It’s clean and the diaphragm looks fine. I put it back together, restarted, same results.

This is where I’m at:
-Fuel and carb are clean.
-The spark plug I tried previously was used and the wrong temp but I figure has 95% ruled out a faulty plug issue.
-Clattery noise, sounds like valve clearance but could also be chain tensioner or something else?
-Wiring - the side cover has been off and on recently to sort out the starter clutch. It’s a real mangle getting the alternator wiring past the oil pipe.

It's such a waste just sitting there, what to do next?

I'm trying to sort it out without going to the shop, although I'll take on board any good recommendations.

I know this is a silly question but when you cleaned the carb did you clean out all the jets?
Had the same thing on my bike (it had sat for awhile) the main jet was nearly blocked. as soon as i cleaned it out it ran fine.

[Staticam]

... did you clean out all the jets?

Well no. The thing was so clean it didn't seem justified. You think I should remove and inspect the main jet and sprayer? (I can't post a diagram at the mo').

[BoristheBiter]

Well no. The thing was so clean it didn't seem justified. You think I should remove and inspect the main jet and sprayer? (I can't post a diagram at the mo').

Yep, i would give it a go. mine was spotless as well but blocked.
What does it run like with the choke on?

[Taz]

Air filter good? Changed spark plug?

[idb]

Blockage in the fuel tank air breather maybe?

[Staticam]

Yep, i would give it a go. mine was spotless as well but blocked.
What does it run like with the choke on?
Fair enough, I'll try cleaning it properly next weekend. Choke is needed for start but runs rich if left on once warm. (I think I know where you are going with this - I'll try it before attemping the clean).


Air filter good? Changed spark plug?
Air filter clean, probably not plug, refer post 12


Blockage in the fuel tank air breather maybe?
Tank is clean. I doubt a tank or breather block could build up a vacuum so quick. If a clean doesn't get me anywhere I'll try with the lid open.

[Staticam]

Tonight's effort. Tank off, carb out, main jet and sprayer removed - spotless. Reassemble. Test - fail. Test with choke full on - fail. By fail I mean it won't rev properly above 3/4 rev range. All up about 40 minutes. Forgot to try with the tank lid open.

Tank is clean (plastic).
Fuel is clean and fresh.
Carb is a Mikuni SE BST 40 (a bit like an SU) and is clean.
Spark plug is used but looks acceptable (light brown coloured). Tried a different plug, also used but one step colder - no difference.

Down to the wire(s) now.

I have had the alternator cover off in the recent past so I have disturbed the wiring harness. From the alternator there are 3 wires to the regulator (all Ye/Bu) and 4 to the CDI (Rd, Bk, Wh and Gn). Can they be checked and how?

How can I test the output of the CDI to coil?
How can I test the coil and it's integral spark plug lead?

TIA, Luke

[idb]

Tonight's effort. Tank off, carb out, main jet and sprayer removed - spotless. Reassemble. Test - fail. Test with choke full on - fail. By fail I mean it won't rev properly above 3/4 rev range. All up about 40 minutes. Forgot to try with the tank lid open.

Tank is clean (plastic).
Fuel is clean and fresh.
Carb is a Mikuni SE BST 40 (a bit like an SU) and is clean.
Spark plug is used but looks acceptable (light brown coloured). Tried a different plug, also used but one step colder - no difference.

Down to the wire(s) now.

I have had the alternator cover off in the recent past so I have disturbed the wiring harness. From the alternator there are 3 wires to the regulator (all Ye/Bu) and 4 to the CDI (Rd, Bk, Wh and Gn). Can they be checked and how?

How can I test the output of the CDI to coil?
How can I test the coil and it's integral spark plug lead?

TIA, Luke

Plug out with lead attached, rest on motor, crank over, there should be a spark.

[Staticam]

Plug out with lead attached, rest on motor, crank over, there should be a spark.

Um, I can't use that method to test at near max rpm.

[idb]

Um, I can't use that method to test at near max rpm.

I'm not sure what that will tell you but if that's what you want I can't see why you couldn't do it one plug at a time.

[Staticam]

I'm not sure what that will tell you but if that's what you want I can't see why you couldn't do it one plug at a time.

A bit tricky cause it's only got one plug! It's a 600 single, four valve.

[idb]

A bit tricky cause it's only got one plug! It's a 600 single, four valve.
oh........

[BoristheBiter]

Tonight's effort. Tank off, carb out, main jet and sprayer removed - spotless. Reassemble. Test - fail. Test with choke full on - fail. By fail I mean it won't rev properly above 3/4 rev range. All up about 40 minutes. Forgot to try with the tank lid open.

Tank is clean (plastic).
Fuel is clean and fresh.
Carb is a Mikuni SE BST 40 (a bit like an SU) and is clean.
Spark plug is used but looks acceptable (light brown coloured). Tried a different plug, also used but one step colder - no difference.

Down to the wire(s) now.

I have had the alternator cover off in the recent past so I have disturbed the wiring harness. From the alternator there are 3 wires to the regulator (all Ye/Bu) and 4 to the CDI (Rd, Bk, Wh and Gn). Can they be checked and how?

How can I test the output of the CDI to coil?
How can I test the coil and it's integral spark plug lead?

TIA, Luke

If it was a car i would say its either the vacuum advance or the timing but i have no idea how your bike is set up.
It still sounds like the carb settings air/fuel mixture as it runs fine until you open the throttle up. 75% throttle is open quite far for a wiring fault and it would generally be picked up even when idling.
Can you run it with the air filter off? listen to noise change when it starts to die. try with choke on and off.
Does it run fine at 50%? what it the rev range for when it starts dieing? is it the same in all gears?

[Staticam]

If it was a car i would say its either the vacuum advance or the timing but i have no idea how your bike is set up.
It still sounds like the carb settings air/fuel mixture as it runs fine until you open the throttle up. 75% throttle is open quite far for a wiring fault and it would generally be picked up even when idling.
Can you run it with the air filter off? listen to noise change when it starts to die. try with choke on and off.
Does it run fine at 50%? what it the rev range for when it starts dieing? is it the same in all gears?

If it was a horse I'd shoot it!

Apart from my checking the carb settings should not be out. It did run fine. Between then and now the only thing that could have been disturbed is the wiring. I suspect that as the revs increase so does the pressure of the smoke in the wires. Because wiring has been pushed around maybe the insulation is breaking down, smoke escapes under pressure.

I can try with the air filter out but the exhaust, Ducati like, is loud, I doubt I'd be able to hear anything. The choke makes no difference. It idles and runs up to 50% maybe more happily in neutral or any gear. When full demand is asked for it's like it hitting a limiter at about 75%. It has no tacho. I built a kitset one but it won't work with the CDI, the trigger voltage is to high? I don't fully understand the alternator/CDI/coil setup to make it work. I wish I did.

[BoristheBiter]

If it was a horse I'd shoot it!

Apart from my checking the carb settings should not be out. It did run fine. Between then and now the only thing that could have been disturbed is the wiring. I suspect that as the revs increase so does the pressure of the smoke in the wires. Because wiring has been pushed around maybe the insulation is breaking down, smoke escapes under pressure.

I can try with the air filter out but the exhaust, Ducati like, is loud, I doubt I'd be able to hear anything. The choke makes no difference. It idles and runs up to 50% maybe more happily in neutral or any gear. When full demand is asked for it's like it hitting a limiter at about 75%. It has no tacho. I built a kitset one but it won't work with the CDI, the trigger voltage is to high? I don't fully understand the alternator/CDI/coil setup to make it work. I wish I did.

I agree just shoot it.

[Staticam]

I've tested for smoke leaking out of the wires, and there wasn't any. Time for a new approach.

The clattery rattle racket it makes while running, while possibly some valve noise, is most likely the timing chain. The tensioner is at full stretch.

If it jumps a tooth would it run, or run noticeably out of whack?
If the chain is flailing round and hitting things, could that be the problem?

[MSTRS]

I've tested for smoke leaking out of the wires, and there wasn't any. Time for a new approach.

The clattery rattle racket it makes while running, while possibly some valve noise, is most likely the timing chain. The tensioner is at full stretch. Not good

If it jumps a tooth would it run, or run noticeably out of whack? Yes to both
If the chain is flailing round and hitting things, could that be the problem?

Or you sure that all valves are closing fully? Reduced compression would have it bogging down.
Change the oil. Capture and strain the old oil and check closely for metal filings. If the camchain is loose enough to touch things...well, you can be assured that it is grinding them away. Had a CB100 do that back in the 70s and before I know what I know because of it.

[Staticam]

Or you sure that all valves are closing fully? Reduced compression would have it bogging down.
Change the oil. Capture and strain the old oil and check closely for metal filings. If the camchain is loose enough to touch things...well, you can be assured that it is grinding them away. Had a CB100 do that back in the 70s and before I know what I know because of it.

I think the valves are closing - I can get a feeler gauge blade in there. I'll do a compression test. There certainly was filings in the oil but that was due to the starter clutch bolts. I haven't looked recently. Somehow I think I knew I should have done the timing chain when the sprag was getting fixed. Take the motor out again I guess...

[Staticam]

Reduced compression would have it bogging down.

Compression test showed up 85psi cold (throttle closed, oops). I don't know what it should be except 7.8:1 ratio.

I took it past a couple of shops to test their ear and get their opinions. First one wanted me to leave it (along with an open cheque book I guess) so they could pull it apart for a closer look. The second thought the valve train might be trashed. Both agreed that it isn't making happy sounds.

I'm getting a price for a timing chain, guides and associated gaskets.

I wish I could just throw another motor at it, if it were just that easy... someone might know what might fits.

[MSTRS]

Compression test showed up 85psi cold (throttle closed, oops). I don't know what it should be except 7.8:1 ratio.



Seems very low. I would expect to see somewhere over 120psi , probably 150-ish
Badly seated valve?