barnett468
Coast to Coast
you can not shift the transs by rotating the rear wheel because the rear wheel wont ritate unless you have around 30 lbs of compression or less . . you should remove the pluugs then rotate the cank with the starter.
Maxes-out around 55mph. 81 CB750 DOHC
- Thread starter Joseph New York
- Start date
That shifter clearly had a large part of the weight of the bike on it while sliding. I'd be willing to put money down that the something is amiss behind that cover.
The shift plate could be off a notch or two, the shift stopper could be bent or separated, or the spindle is bent, broken or separated from shifter shaft. The shift plate moving is not hard to do and would make sense. When the PO thinks he's in 5th, he's actually in 3rd or 4th. A check for all 5 gears and neutral is in order, no doubt.
The shift plate could be off a notch or two, the shift stopper could be bent or separated, or the spindle is bent, broken or separated from shifter shaft. The shift plate moving is not hard to do and would make sense. When the PO thinks he's in 5th, he's actually in 3rd or 4th. A check for all 5 gears and neutral is in order, no doubt.
barnett468
Coast to Coast
Nope because he will be trying to overcome the compression of the engine which can be done but it's ridiculous to do it that way as it requires a bit of strength . . take 3 minutes to remove the spark plugs, its not that hard to do.
Joseph New York
Active Member
Side panel and plugs coming out tomorrow when I test my clutch/gears. Will take pics and vids to get your opinions! Tonight going for a long ride and report RPMs/MPH to gear. I just put on a shiny new tach.barnett468 said:
Just dyn synced carbs and no vacuum leaks at manifold or podsJimmyD750 said:
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barnett468
Coast to Coast
TACHS work better when they are shiny.
Joseph New York
Active Member
My last one was shiny, but smashed to shiny bits
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Joseph New York
Active Member
OK, a lot to cover...
1) My ears don't seem to be a good tach for this bike :/ Yesterday I added a new tach and ran some highway tests. My previous assumptions of 7/8k RPMs @ 55mph was grossly exaggerated. In 5th she seems to cruise at around 4.5k going 55mph. Perhaps it's the vibrations that throw me off because it's pretty shaky at 55 so I'm assuming I'm pushing her harder than I may be. I recently rebuilt the forks/added clip-ons, etc. so I'll have to do some adjusting to stabilize. But that's another issue. I don't seem to be alone though in my lack-of-speed concerns: http://forums.sohc4.net/index.php?topic=26964.0 they seem have the same thoughts. I do have to mention that I hit a few false neutrals yesterday and when I did once, the gears sounded as if someone threw in a marble. The rattling was loud while it was spinning. Sounded like a cog tooth or piece of chain rattling around. Not a pleasant sound to hear on the open road... This obviously made me more anxious to pop off the clutch cover and find out what's going on, but then this happened:
2) After I parked her on the sidewalk last night, I left for a while and when I returned to work on it some more, the bike was on it's center-stand, and moved to the street. In NYC, your bike gets knocked over a lot. It really sux but it comes with the territory. Well after inspecting the damage I expected to see, the right side had scrapes on the tank, the right handlebar end was grounded down making the throttle sleeve stick, foot peg grinded up, and the break lever completely snapped off near the base, and missing. On the left side, no real damage, but oddly enough the gas tank cap's tear marks are in that direction. Whenever my bike has been moved from my return, the first thing I look for is the gasoline tear marks, and their direction is the opposite side. Explain that sh*t. Finally on the right side on my exhaust there's a green liquid, still wet and bubbling. Not sure if that came from the battery, Predator, or what!?
3) Back to the lack of speed: After riding for a few hours on the highway yesterday, the engine's sound changed. Ya Know the sound when your engine is starving and you may be running out of gas? Well on the way back I started to get that sound and the idle stability seemed to be less. At higher RPMs it sounded decent though. After she cooled down I ran the engine for a bit to take her temperature by touching the exhaust. (I have exhaust wrap) The first cylander's exhaust seems cooler and and I'm suspecting it's not firing now. It's also the same cylinder that stopped firing after the accident if I remember correctly. This has me thinking, maybe it's not a gear issue entirely, but what if it's compression? I asked the garage to check compression but I'm doubting they did. I have a compression tester and when I remove the plugs to test the shifting, I'll do a test.
Maybe the prob is my clutch, maybe the engine, maybe it's nothing, maybe it's me and I just need to ride her harder. Regardless I feel that my 750 is the slowest of my CBs and I feel it's worth the attention.
I really appreciate all your help, and will continually update the post with progress and test results from all your suggestions. Some a-hole knocking over my bike has effected my wrenching schedule so please be patient wit me.
Cheers!
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1) My ears don't seem to be a good tach for this bike :/ Yesterday I added a new tach and ran some highway tests. My previous assumptions of 7/8k RPMs @ 55mph was grossly exaggerated. In 5th she seems to cruise at around 4.5k going 55mph. Perhaps it's the vibrations that throw me off because it's pretty shaky at 55 so I'm assuming I'm pushing her harder than I may be. I recently rebuilt the forks/added clip-ons, etc. so I'll have to do some adjusting to stabilize. But that's another issue. I don't seem to be alone though in my lack-of-speed concerns: http://forums.sohc4.net/index.php?topic=26964.0 they seem have the same thoughts. I do have to mention that I hit a few false neutrals yesterday and when I did once, the gears sounded as if someone threw in a marble. The rattling was loud while it was spinning. Sounded like a cog tooth or piece of chain rattling around. Not a pleasant sound to hear on the open road... This obviously made me more anxious to pop off the clutch cover and find out what's going on, but then this happened:
2) After I parked her on the sidewalk last night, I left for a while and when I returned to work on it some more, the bike was on it's center-stand, and moved to the street. In NYC, your bike gets knocked over a lot. It really sux but it comes with the territory. Well after inspecting the damage I expected to see, the right side had scrapes on the tank, the right handlebar end was grounded down making the throttle sleeve stick, foot peg grinded up, and the break lever completely snapped off near the base, and missing. On the left side, no real damage, but oddly enough the gas tank cap's tear marks are in that direction. Whenever my bike has been moved from my return, the first thing I look for is the gasoline tear marks, and their direction is the opposite side. Explain that sh*t. Finally on the right side on my exhaust there's a green liquid, still wet and bubbling. Not sure if that came from the battery, Predator, or what!?
3) Back to the lack of speed: After riding for a few hours on the highway yesterday, the engine's sound changed. Ya Know the sound when your engine is starving and you may be running out of gas? Well on the way back I started to get that sound and the idle stability seemed to be less. At higher RPMs it sounded decent though. After she cooled down I ran the engine for a bit to take her temperature by touching the exhaust. (I have exhaust wrap) The first cylander's exhaust seems cooler and and I'm suspecting it's not firing now. It's also the same cylinder that stopped firing after the accident if I remember correctly. This has me thinking, maybe it's not a gear issue entirely, but what if it's compression? I asked the garage to check compression but I'm doubting they did. I have a compression tester and when I remove the plugs to test the shifting, I'll do a test.
Maybe the prob is my clutch, maybe the engine, maybe it's nothing, maybe it's me and I just need to ride her harder. Regardless I feel that my 750 is the slowest of my CBs and I feel it's worth the attention.
I really appreciate all your help, and will continually update the post with progress and test results from all your suggestions. Some a-hole knocking over my bike has effected my wrenching schedule so please be patient wit me.
Cheers!
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barnett468
Coast to Coast
OK, bummer about the new. York a holes.
Again, based on your description, your clutch us NOT slipping.
Count the gear teeth as suggested.
If it vibrates now but did not vibrated before, the end of the crank may be bent . . if it is missing on one cylinder it will also vibrate some.
When you do a compression test remove the other plug caps and lay the suspect plug on the head and. Crank it over and see if it sparks.
Again, based on your description, your clutch us NOT slipping.
Count the gear teeth as suggested.
If it vibrates now but did not vibrated before, the end of the crank may be bent . . if it is missing on one cylinder it will also vibrate some.
When you do a compression test remove the other plug caps and lay the suspect plug on the head and. Crank it over and see if it sparks.
Correct me if I'm wrong with an inline four, but typically with twins "shaky" can be a signal of out of sync carbs. Not sure if you mean it vibrates a lot or just a condition of suspension, etc. Having a cooler exhaust can also be a sign of that condition.
barnett468
Coast to Coast
deviant said:
Yes that can also contribute to it but usually not to the extent I am guessing he means but this should be checked anyway it regardless just as a matter of properly tuning the bike
Joseph New York
Active Member
barnett468 said:
Sorry for the delay.
I just synced the carbs, they're inline. Carb #1 may have a dirty pilot jet that's causing it's cylinder to stop firing at idle. More on that below. The shaking is more like a numbing vibration (I think) from the suspension or break. Not sure but I'll smooth it out along with some other projects I got going with the 750.
#1 not firing...
So I checked for sparks on #1 and it was firing up nicely sitting on the head. Checked compressions on #1 & #4 and try are both at 85psi. I replaced the plug anyways, and did a test run and it wasn't firing still. Parked it, ran it again harder and it's now firing
I should clean the carbs, but I'm currently cleaning my 650's rack and will get to it ASAP. Picking up a sixer of carb cleaner tomorrow.Now that she's running on all four again, I'm going to pop open my clutch cover and try and see what's going on. The rattling piece in my gears was bad on my last test run. Don't want to ride anymore until it's resolved.
I'll be back, thanks!
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barnett468
Coast to Coast
.
well, if your compression really is 85 lbs or anything under 120, your engine is done.
remove the top end and fix it.
spray a bit of carb cleaner in the ports in the head the lift it up or ti;lt one side up and look at the valves to see if they are leaking . . unless they are heavily leaking like a geyser, you need to rebuild the top end.
if your gauge is cheap, you should try a high quality gauge first to verify the compression.
the throttle should be at least half way open during the test.
well, if your compression really is 85 lbs or anything under 120, your engine is done.
remove the top end and fix it.
spray a bit of carb cleaner in the ports in the head the lift it up or ti;lt one side up and look at the valves to see if they are leaking . . unless they are heavily leaking like a geyser, you need to rebuild the top end.
if your gauge is cheap, you should try a high quality gauge first to verify the compression.
the throttle should be at least half way open during the test.
Joseph New York
Active Member
My bad I didn't mention the gauge is crap, and that I was really testing consistency from #1; I also didn't pull the plugs / WOT. But now you have me thinking I need to do a real test. Originally I was thinking that low compression could be causing my lack of speed. That possible? I'll do a real compression test with a different gauge if one becomes avail. I'll be back with 4 accurate numbers before removing the top end.
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barnett468
Coast to Coast
.
well you said it would do a wheelie and pull your arms out of your sockets it you revved it up and dumped the clutch so based on your description it does not sound like it has low compression, but since it is a free and easy thing to test, it is certainly something i would do.
well you said it would do a wheelie and pull your arms out of your sockets it you revved it up and dumped the clutch so based on your description it does not sound like it has low compression, but since it is a free and easy thing to test, it is certainly something i would do.
Did you test compression wet by dropping a few drops of oil into the spark plug hole, as well? You should do both.
Joseph New York
Active Member
barnett468 said:
I've always been curious about if low pressure (with enough to fire) could effect power or torque. I've always just made sure they were all consistent.
deviant said:
Dry, but it wasn't a real test. I'll do a wet and dry test shortly. I'm sure it's good to know the pressures especially with an engine that's been dropped hard on both sides.
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Joseph New York
Active Member
Damn, Im on the bike now and the first cylinder isn't firing again. I'll bet the plug is sparking. Should I pull the carbs??
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