Topic: 750 71K vs 75F clutch. underpowered right now.

[cheftuskey121]

quick question. is there a difference in stack height between a 1971 K1 clutch and a 1975 F0 clutch? when I got my "new" F0 motor it had the clutch basket and steel plates but no cork plates in it. I transferred the entire K1 clutch (basket, plates, springs etc) to the f) motor to make it as easy transition since it worked in the K1 motor. when I ride around in 5th gear I need to be at 5000rpm just to go 60mph. this is off. it feels like the clutch is permanently slipping, as if the stack height isnt high enough, causing me to constantly be under powered. this makes sense yes? I also need to add that the clutch is not slipping in the normal sense. I can get the engine up to 7000+ rpms under riding conditions. only when I am accelerating fast and I change gears it feels like it doesn't catch right away and takes a second before I get power again. so it's slipping but not like I have read described before. its not a sudden loss of power, its like a constant loss of a small amount of power.

I am just looking for direct experience, logic, or speculation before I tear into it. its good to note I also have a cycle x clutch kit with new steel and cork plate along with the heavy duty springs. perhaps I just need to build a new clutch? the cycle x kit includes an extra plate for those models that require it. I am scared of making the stack too high and cracking that lifter plate. I have no "correct" F0 clutch to compare it to, hence the post. insight is welcome! thanks.

[scharny61]

I'm experiencing much the same problem right now. The clutch basket part numbers for these two years are different. You would be advised using the original clutch basket IMO.

[bjbuchanan]

It isn't gonna be a thick enough stack. If you dredge up any of the old, and pretty thorough, problem threads they come up pretty fast when mixing and matching like that

http://forums.sohc4.net/index.php?topic=51486.0;nowap

http://forums.sohc4.net/index.php?topic=111938.0

http://forums.sohc4.net/index.php?topic=123494.0

There is a couple threads. I'm having trouble finding the money thread I want, it is like six pages and you will be a clutch master for 750's after reading it

[cheftuskey121]

Thanks bj that's what I'm thinking. Just gonna rebuild with the cycle x kit. I've been reading up on it. Just have to peer inside to see what I have as far as metal plates go. In the F0 clutch basket there are only 6 steel plates all the same. No double plate like I've read about....am I missing this?

[HondaMan]

When mixing and matching, here's a rule of thumb that helps: if the top (spring) plate is flush or slightly inside the ends of the basket "fingers", you're pretty close to correct stack height. If it is letting the top plate's tabs stick out of the basket at all, it is too tall. If it sits down inside the basket by more than a plate thickness, something is missing.

Keep in mind, you can make several different stack arrangements. For example, you can use an old K0 steel "#1 plate" to add thickness to the stack for a 6-plate pack if the thin plate is too little, or an extra fiber plate is too much. You can also use the taller K3-K6 hub and use an extra steel plate (top or bottom) to make the height come out right: this makes a 6-fiber-plate clutch in the end.

(The F0 clutch basket is different: it uses a top plate with wider tabs and slanted cork blocks, to induce slip. That one requires the F hub as well, and the dual-steel plate, or the thicker Gold Wing spacer plate, to make the stack height.)

[cheftuskey121]

When mixing and matching, here's a rule of thumb that helps: if the top (spring) plate is flush or slightly inside the ends of the basket "fingers", you're pretty close to correct stack height. If it is letting the top plate's tabs stick out of the basket at all, it is too tall. If it sits down inside the basket by more than a plate thickness, something is missing.

Keep in mind, you can make several different stack arrangements. For example, you can use an old K0 steel "#1 plate" to add thickness to the stack for a 6-plate pack if the thin plate is too little, or an extra fiber plate is too much. You can also use the taller K3-K6 hub and use an extra steel plate (top or bottom) to make the height come out right: this makes a 6-fiber-plate clutch in the end.

(The F0 clutch basket is different: it uses a top plate with wider tabs and slanted cork blocks, to induce slip. That one requires the F hub as well, and the dual-steel plate, or the thicker Gold Wing spacer plate, to make the stack height.)

thanks hondaman. so I CAN use my K1 basket, and replace the old plates with the new cycle x plates? just as long as I get the stack height correct? I am missing the dual steel plate for the 75F clutch, and I would like to use the new clutch plates I bought ages ago. checking my K1 clutch there are 7 fiber plates-they are first and last, and there are 6 steel plates in between, that's all. the cycle x fiber plates have slant cuts, which way should they face when looking at the clutch assembly from outside in (normal viewing point)
? // or \\ ?

[MRieck]

When mixing and matching, here's a rule of thumb that helps: if the top (spring) plate is flush or slightly inside the ends of the basket "fingers", you're pretty close to correct stack height. If it is letting the top plate's tabs stick out of the basket at all, it is too tall. If it sits down inside the basket by more than a plate thickness, something is missing.

Keep in mind, you can make several different stack arrangements. For example, you can use an old K0 steel "#1 plate" to add thickness to the stack for a 6-plate pack if the thin plate is too little, or an extra fiber plate is too much. You can also use the taller K3-K6 hub and use an extra steel plate (top or bottom) to make the height come out right: this makes a 6-fiber-plate clutch in the end.

(The F0 clutch basket is different: it uses a top plate with wider tabs and slanted cork blocks, to induce slip. That one requires the F hub as well, and the dual-steel plate, or the thicker Gold Wing spacer plate, to make the stack height.)

Mark...the original F basket and hub do not require the spring loaded double steel plate. The stack can be modified to accept it. My 75F never had a dual steel plate (like the GL's). The top friction plate tabs are different. What do you mean by the "GL spacer" plate? You are talking about the riveted spring loaded plate which you already mentioned.

[cheftuskey121]

When mixing and matching, here's a rule of thumb that helps: if the top (spring) plate is flush or slightly inside the ends of the basket "fingers", you're pretty close to correct stack height. If it is letting the top plate's tabs stick out of the basket at all, it is too tall. If it sits down inside the basket by more than a plate thickness, something is missing.

Keep in mind, you can make several different stack arrangements. For example, you can use an old K0 steel "#1 plate" to add thickness to the stack for a 6-plate pack if the thin plate is too little, or an extra fiber plate is too much. You can also use the taller K3-K6 hub and use an extra steel plate (top or bottom) to make the height come out right: this makes a 6-fiber-plate clutch in the end.

(The F0 clutch basket is different: it uses a top plate with wider tabs and slanted cork blocks, to induce slip. That one requires the F hub as well, and the dual-steel plate, or the thicker Gold Wing spacer plate, to make the stack height.)

Mark...the original F basket and hub do not require the spring loaded double steel plate. The stack can be modified to accept it. My 75F never had a dual steel plate (like the GL's). The top friction plate tabs are different. What do you mean by the "GL spacer" plate? You are talking about the riveted spring loaded plate which you already mentioned.

that makes sense Mike, as I measure both the K1 basket-hub and 75F basket-hub stack (with no plates inside) and they are almost identical. it seems they are the same part so even if I had the double plate it would not work...hmm. I put the new cycle x plates in place and my basket stack went from 52.45mm to 53.30mm. I am sure some of that extra space is the "new" oil swollen plates? I am going to try and put everything back in place. unfortunately I won't be able to test until tomorrow.

again it was not "slipping" as most of these "clutch slipping" threads are. just consistently underpowered as if its just a smidge off....

[Jerry Rxman Griffin aka MuthaF'er]

That double GL metal plate did not appear in F's until LATE in the 76 model year at serial number, as taken from my copy of The Wrench dated 12/8/1976, "starting with the following engine numbers: CB750 E #2700014 and CB750F E #2557523."

From my Honda brand shop manual 2700001 was a 77 K. 2557523 would have been an end of the year F1. My other parts manual taken from a fiche is dated 4/93. It shows the 76 has engines 2525094 to 2563530. It shows the double disc added at 2558989. So 2558989 out of 2563530 is when the GL disc update happened.

Not to worry Chef, your 75 and my 75 did NOT have that GL double disc from the factory. Mine is original owner and I know it hasn't been rigged up by anyone. Mine does now  as I've used a 78 complete unit in it. The field upgrade is another option which I'll do with my 75 clutch when it goes into that 78 engine.   

[cheftuskey121]

That double GL metal plate did not appear in F's until LATE in the 76 model year at serial number, as taken from my copy of The Wrench dated 12/8/1976, "starting with the following engine numbers: CB750 E #2700014 and CB750F E #2557523."

From my Honda brand shop manual 2700001 was a 77 K. 2557523 would have been an end of the year F1. My other parts manual taken from a fiche is dated 4/93. It shows the 76 has engines 2525094 to 2563530. It shows the double disc added at 2558989. So 2558989 out of 2563530 is when the GL disc update happened.

Not to worry Chef, your 75 and my 75 did NOT have that GL double disc from the factory. Mine is original owner and I know it hasn't been rigged up by anyone. Mine does now  as I've used a 78 complete unit in it. The field upgrade is another option which I'll do with my 75 clutch when it goes into that 78 engine.

thanks Jerry.....so then, that actually helps less.....why am I only doing 60mph at 5k in 5th gear? and why does the bike feel underpowered. the ONLY thing that has changed is the actual engine from 71K to 75F. sprockets are same (17/48). the engine can't be THAT underpowered naturally...can it? maybe I just didn't have my clutch adjusted properly? 

[Jerry Rxman Griffin aka MuthaF'er]

I would expect ~ 70mph on the speedo @ 5000 with the 17/48. The clutch shouldn't have any effect on that unless it's slipping and then the speed would be inconsistent.

Did you disassemble the K clutch or transfer it whole?

Does it have all the parts as compared to a parts fiche?

Perhaps stronger springs would help? but if it didn't slip before it shouldn't now. Or as you say, build the new clutch.

What oil are you using? Car or bike? Synthetic or dino?

What size front tire are you running? (speed thing unrelated to slippage)

Do you have another speedo to try?

The 75F engine is one of the better ones and is/should be pretty strong. Are we sure it's a 75 F engine? What's the s/n? CB750e-2500002 to 2515054 from memory (not at home)

Here's some pics



75 750F clutch with 7 discs and no double metal GL metal disc. If it fits together like this with a gap and the plates slide back and forth that is wrong. Remove the pressure plate and rotate it 90 degrees then put back together. You'll see where the teeth will have to mesh.



It should look like this (ignore the double plate you see. this is the later clutch pack). Snug fit. Pressure plate was rotated 90 degrees and reinserted.



When installed the 'tabs' should be inset within the basket like such and not sticking out further.



I'm not at home so l'm somewhat limited as to resources. I'll be back Sunday for a few days and I can go to the garage and look at my references then. Maybe some of this will help. This damn clutch thing drove me crazy too for a while.

OR it could be an adjustment thing 
 

[cheftuskey121]

thank Jerry. good stuff here. yes I agree 5000 rpm in 5th is 70 with 17/48, because that is what the K1 engine put out on the same bike. let me answer your questions.
I transferred the K clutch whole. including plates, lifter plate/screws, springs, washer, tab, nut. I did not transfer the clutch cover and mechanism yet.

it looks like all of the parts are there according to the fiche. at least it was in the K1, and it rode and shifted fine.

I plan on putting in the cycle x hd springs with the new plates. it didn't "slip" like say I goosed it and at 4k it slipped...its not like that. its like when I am accelerating fast and shift up it doesn't just go into the next gear with full power, it's as if it is slipping and take a second to get the power back. and then obviously I am a whole 1000rpm off in 5th gear. the speed feels right, but the engine is working harder

I use rotella t5 15w40 dino oil, seems to be highly recommended and used around here. it worked flawlessly in the K1 engine, and works great in the F3 engine I have.

front is stock 19" rim with bt45 tires(same as before my wreck)

I guess I could try another speedo (I have another K1 speedo and I could use the F speedo) BUT it was the same speedo from the other engine. the only thing different is this engine. all things from before are the same and 5000rpm in 5th was 70mph

the engine number is 2501079 so its one of the earlier ones according to those numbers.

according to that diagram posted I do not have the funky looking fiber plate near the front of the stack (closest to engine cover) or the plain metall plate at the back of the stack (closest to engine). not sure if that's for a different model. according to YOUR pictures mine looks like that. with the pressure plate flush of course, and it lines up with the hub fingers like that too. it all looks the same! gahhh, maybe my clutch adjustment is just off? this is strange.

tomorrow after my new plates have been soaking in oil I'll put the new plates in the 75F basket (and put the K1 clutch back in the K1 engine) and try from there. thanks to all so far. I'll update as I find out more

[seanbarney41]

Do the f motors use a different tach ratio?

[Jerry Rxman Griffin aka MuthaF'er]

Your's should be the top diagram. 6 normal discs and that 1 different on the outside end with 6 metals (no double like it shows that you can insert for the upgrade) for a total of 7 fiber discs.

Cone washer behind the big nut that holds everything on pointed outwards?

I have some other pics of the 2 different size 25mm washer that go behind the basket on the shaft and pictures of the early and late shafts if you need those.

Oil seems ok. Wheel/tire size seems ok.

Not sure I understand this - "its not like that. its like when I am accelerating fast and shift up it doesn't just go into the next gear with full power, it's as if it is slipping and take a second to get the power back. and then obviously I am a whole 1000rpm off in 5th gear. the speed feels right, but the engine is working harder"

This doesn't sound like a speedo. We're ruling possibilities out now.

Your's is early January. My bike is January also - 1606 and engine 1954 and it ran like a scalded ass monkey!

What bike is this in? What carbs are you using? What jetting? Stock airbox?   


 

[Jerry Rxman Griffin aka MuthaF'er]

Do the f motors use a different tach ratio?

Same

[cheftuskey121]

Jerry, what I mean by that is on my F3, when I accelerate hard and shift up, it goes into the next gear and I instantly have power and continue accelerating. on Yolanda, where the 75F motor is in (K1 motor used to be) the same power is not there when accelerating and shifting up. it seems like its underpowered, like the clutch isn't 100 released. as far as the lever goes it is, because I have the clutch release point set early from the lever....just let it out a whisker and power start to transfer

so I know its not the lever adjustment.

the cycle x kit includes 8 fibers all identical, I planned on only using 7 fibers, but they all look the same. in that diagram the outside one looks slightly different. not sure if its supposed to be different or not but cycle x did not provide a different looking one.

the cone washer is concave inwards toward the engine, convex faces out, I read about that, so its correct.
 this engine is the replacement engine for my K1. my engine was damaged in my wreck so it was easier to source a new one. stock carbs for a K1 with stock jetting for a K1 (120/40) stock airbox with a K&N filter, HM341 pipes. my plugs used to be tan leaning more towards lean. right now they number 4 plug is a little lean, and the number 1 is a little rich. can't remember 2&3. I can check tomorrow. this bike is all about stock stock stock, haha.

[Don R]

 I'm sure you're aware of the gear ratio difference in an F trans right? For highway riding I prefer 18/48 in my F1. With the F gears and the same sprockets it should accelerate better not worse though.

[cheftuskey121]

Yes don I'm aware. My F3 accelerates like a bat out I hell compared to the k1 motor. This F0 (am I saying that right?) motor feels like a sunday stroll. 

[HondaMan]

When mixing and matching, here's a rule of thumb that helps: if the top (spring) plate is flush or slightly inside the ends of the basket "fingers", you're pretty close to correct stack height. If it is letting the top plate's tabs stick out of the basket at all, it is too tall. If it sits down inside the basket by more than a plate thickness, something is missing.

Keep in mind, you can make several different stack arrangements. For example, you can use an old K0 steel "#1 plate" to add thickness to the stack for a 6-plate pack if the thin plate is too little, or an extra fiber plate is too much. You can also use the taller K3-K6 hub and use an extra steel plate (top or bottom) to make the height come out right: this makes a 6-fiber-plate clutch in the end.

(The F0 clutch basket is different: it uses a top plate with wider tabs and slanted cork blocks, to induce slip. That one requires the F hub as well, and the dual-steel plate, or the thicker Gold Wing spacer plate, to make the stack height.)

Mark...the original F basket and hub do not require the spring loaded double steel plate. The stack can be modified to accept it. My 75F never had a dual steel plate (like the GL's). The top friction plate tabs are different. What do you mean by the "GL spacer" plate? You are talking about the riveted spring loaded plate which you already mentioned.

Yes, they can be altered to fit, and in all sorts of ways. Sometimes folks just want "extra grip", so they take out the dual-springy plate thing and install, for example, a set of the more modern corks plates and steel plates (which are thinner, like .131" new)  so as to get an extra plate set in the stack. I've done this, too, but I ended up selecting between the corks of 3 sets of plates I had bought, to get enough thin ones to pull it off, and you must use the thinner steel ones, too.

Conversely: if you have a stock engine and don't ride hard, switching a later 7-plate clutch "back" to just 6 plates will make it disengage to Neutral easier when hot. Just install the steel plate first and flip the stack order on the longer hub. Sometimes, that's a good idea, too.

[Jerry Rxman Griffin aka MuthaF'er]

Couple things to think about.

Yes that 1 single disc is different. Wish I had one to play with NOW. I can take a peak before the Broncos play Sunday when I get home and report back. Anyone have this answer?? Tabs may be bigger to lock in better?? I do not remember the deal. My 75 clutch pack is on the bench BUT it has Barnett discs in it. I MAY have the stock 78 K discs  to check.

Stock F/F1 jetting is 105 mains, middle needle position and 40 slows. Could be part of the problem. I'm THINKING the carbs are identical (??) except for the needle jet/needle pair which is a 392 part. Any other input on the K carbs from anyone??

With that in mind you are running different exhausts than the F which can affect the jetting requirements. I would discount the K & N for now.

"Accelerating and shifting up" Full on power, slight throttle, middle of the road?? RPMs?? Might be a little rich at the transition rpm range between the needles and mains. That may be more evident at lower rpms and easier throttle operation since it's not sucking air as hard.

[cheftuskey121]

I am unsure about the carbs, but I was under the impression that if all system were the same as before, the engine would not change much, since my input (carbs) and output (exhaust are the same). I seem to be getting decent plugs. I have yet to really open the throttle 100% so the main jets have not even seen any real use. curious though. I used the K1 advancer since I transferred over the pamco from the K1 motor. maybe I am advancing too early. could that play a role?

something I noticed is when the bike is on the center stand in neutral and I rev up, my throttle only moves slightly and the rpms (both on the gauge AND to my ears) jump VERY fast. on the F3 you have to twist the throttle good to get it to rev up. I can't remember how the K1 engine was, but I am telling you I barely touch the throttle and it revs up high too fast (or at least faster than it should be revving) this account for anything?

[Jerry Rxman Griffin aka MuthaF'er]

Can't compare a F2/F3. Wish I had one though. It has a different top end too just as the K1 is different than the F0.

The F0 vs the K1 has slightly higher compression, different head and different cam plus the exhaust. Might be worth it to play with the mains. Easy to do.

They never rev TOO fast  unless you miss a shift at top rpm! Sounds like you need to twist the throttle and see what it does. May be the plugs are loading up a little with the 120's? And only way/best way to read the plugs is to nail the throttle and run up the rpms, hit the kill switch and pull in the clutch at the same time. Coast down and pull the plugs. 5000 rpms, same scenario. I use 3rd gear since it'll/should get close to 100mph at the top of the redline.

Do you know what clip position the needles are set at?

I don't know that there were any differences in advancers?? ANYONE?? I'd need my 2 parts books to check.

Friday night. Bar time for food and drink