1977 CB750 F2 Super Sport
- Thread starter rafanomenon
- Start date
rafanomenon
Been Around the Block
matt365 said:I used a rubber mallot on mine. I'd try that rather than the hammer; seems to dimple a little too much.
This way there's a lot less bondo needed. Your build is really coming along quick!
Man nice work on the tank! Another 750F! With the Comstars! Man I'm lovin it...
Was the rubber mallet accurate? I'm going for a little more of a subtle dent, so i wanted to try something smaller than a huge mallet. A lot of what I've read is people not getting that accurate of a dent with the rubber mallet because of how much give it has, so I wanted to try something with a little more sharp of a contact point. You're right though, it does leave a lot of dimples. maybe i'll try a combo of both?
I'm going into work early today so I can leave early. Then it's straight home to get working on stripping the paint off the actual tank, and pounding the dents. Pictures soon!
Johnny5
Been Around the Block
Bike is looking great!
As I was reading, I knew the 145 main jets would be too large. Too bad I didnt read this sooner I could have saved you some time. I run 130 mains on my 750 and it's perfect in high rpms. Pulls like a champ.
Yeah, always use a rubber mallet for the knee dents. The metal is so soft and thin, it'd be easy to punch through or weaken the structure too much. Here's my bike so far. Knee dents just take patience with the bondo and sanding.
Anyway, nice job! Keep up the good work.
As I was reading, I knew the 145 main jets would be too large. Too bad I didnt read this sooner I could have saved you some time. I run 130 mains on my 750 and it's perfect in high rpms. Pulls like a champ.
Yeah, always use a rubber mallet for the knee dents. The metal is so soft and thin, it'd be easy to punch through or weaken the structure too much. Here's my bike so far. Knee dents just take patience with the bondo and sanding.
Anyway, nice job! Keep up the good work.
rafanomenon
Been Around the Block
Johnny5 said:Bike is looking great!
As I was reading, I knew the 145 main jets would be too large. Too bad I didnt read this sooner I could have saved you some time. I run 130 mains on my 750 and it's perfect in high rpms. Pulls like a champ.
Yeah, always use a rubber mallet for the knee dents. The metal is so soft and thin, it'd be easy to punch through or weaken the structure too much. Here's my bike so far. Knee dents just take patience with the bondo and sanding.
Anyway, nice job! Keep up the good work.
Man those dents look awesome! I figured the majority of time on denting was on bondo and sanding/shaping. The tank just dents too unpredictably. I got moving on the tank last night using a deadblow hammer instead of the pointed metal one. I knew I should've stuck with the pointed metal one because the deadblow wasn't accurate enough. The bottom of the tank dented right where it starts to taper down, so now I'll have to do some crazy shaping work with the bondo to get it the way I originally wanted. I was too pissed to take photos, but i'll make sure to do it tonight so I can post them here.
JRK: I saw those hammers on the shelf at a local hardware store here in Seattle. Something told me to get a deadblow, which worked for some people. Guess it's just trial and error, and whatever works for each individual project. ???
As far as the jets go, I think I'm still running a tad on the rich side. I may fine tune and bump down to 132 or 130. Another trial and error process that depends solely on your bike's setup. A buddy in my club has a 850 big bore kit on his 750 with the same air pods and a Mac exhaust with a single baffle (it comes double stock) and he runs 145 mains
. So much for fuel economy... he has to fill up every 80 miles.As soon as I get it dialed I plan to sync, which I've heard is essential. Just having too much fun riding! ;D
rafanomenon
Been Around the Block
Sidenote: I started sanding, and noticed some Bondo work from the PO. That stuff is tough to sand through, and I was using a palm mouse sander and pressing pretty hard. My question is, do you have to sand to bare metal for the Bondo to adhere correctly? Also, what prep chemical or product do you guys use to clean the surface before bondo and paint? Good ol' soap and water?
Thanks!
Thanks!
Johnny5
Been Around the Block
If there's old bondo, I'd sand away as much as you can. You dont need bare metal for the bondo to stick. It'll stick to other layers of bondo, and primer no problems. Dawn dish liquid is good. Mineral spirits is better. Let it dry well before applying the bondo. Use like 80 grit sandpaper for your first couple rounds of shaping the bondo. It'll cut fast and get your basic shape faster. Then go to 150-250 as you get closer.
For my knee dents, I used the yellow and black double rubber mallet from Harbor Freight in a couple posts above. Worked well.
I run a 4-1 Mac, Emgo Pods, 130 mains, stock slow jets, 2 turns out on the air screw, 1.5 notch on the needle. Yep, I put a little washer on top of the circlip to make it on the 1.5 position. Talk about fine tuning!
For my knee dents, I used the yellow and black double rubber mallet from Harbor Freight in a couple posts above. Worked well.
I run a 4-1 Mac, Emgo Pods, 130 mains, stock slow jets, 2 turns out on the air screw, 1.5 notch on the needle. Yep, I put a little washer on top of the circlip to make it on the 1.5 position. Talk about fine tuning!
rafanomenon
Been Around the Block
Great. Thanks for the tips! I'm picking up some aircraft stripper tonight (that sounds kinda dirty) and plan on getting as much paint and crud off the tank as possible before resanding and Bondo. I've got a spare 750F tank coming in, so if this one doesn't turn out, it's back to pounding!
Wow, you did fine tune that sucker! I was going to move to 2 notches on the needle, as it kind of gargles when the throttle snaps open from the low range. I wish needles were as easy to adjust as jets :
If you read my previous post, I finally had to do away with the stock carbs from the '77 750F. Those were a bitch to deal with. I traded a buddy an F-tank for an older set from a K-model. 135 mains. 45 slows. Stock needle and air screw rotations. Aside from running a tad rich, and the occasional bog in the low range, I couldn't be happier!
Wow, you did fine tune that sucker! I was going to move to 2 notches on the needle, as it kind of gargles when the throttle snaps open from the low range. I wish needles were as easy to adjust as jets :
If you read my previous post, I finally had to do away with the stock carbs from the '77 750F. Those were a bitch to deal with. I traded a buddy an F-tank for an older set from a K-model. 135 mains. 45 slows. Stock needle and air screw rotations. Aside from running a tad rich, and the occasional bog in the low range, I couldn't be happier!
rafanomenon
Been Around the Block
JRK5892 said:
I remember reading that from a previous post of yours, too. Great tips! How long do I leave the gel on there? After sanding, I noticed 3-4 coats of different colors + a clear after the original. 2 of those coats are from my indecisive self going from black to primer
Johnny5
Been Around the Block
JRK, Good tips on the stripper. I use an old paint brush and slathered the stripper all over the tank. Walk away and let the stripper do its job.
Rafan,
The older K carbs are a pain compared to the later (77-78) K carbs. I dont know if they're different from the F carbs or not though. One thing about the pod setups and these SOHC engines is that some of the low throttle response is lost when they are added to the mix. Definitely wont rev like the newer style bikes on the low end. With careful jetting, it'll get close. But the motor doesnt like to have the throttle cracked open really fast.
Rafan,
The older K carbs are a pain compared to the later (77-78) K carbs. I dont know if they're different from the F carbs or not though. One thing about the pod setups and these SOHC engines is that some of the low throttle response is lost when they are added to the mix. Definitely wont rev like the newer style bikes on the low end. With careful jetting, it'll get close. But the motor doesnt like to have the throttle cracked open really fast.
rafanomenon
Been Around the Block
Johnny5 said:
Things I hate about the F-carbs:
- Accelerator pump (kinda cool, actually)
- Press-in jets that wouldn't come out
- Hard to access idle-air screws
- Hard to access main throttle screw
- Choke cable instead of lever
- Push/pull throttle cable layout
- Need phillips head to remove float bowl covers
all of which tested my last nerve when it came to fine tuning. I haven't had any problems so far with the K-model carbs, and they do what they need to do. I'm pretty sure the low-range problem can be fixed by adjusting the needle clips or slow jets, maybe go from 45 to 48, or 50.
Tapered needle. Snap open throttle. Slight bog and popping = needs more fuel faster. Some people swear by the 77-78 F-model carbs though. They just weren't working for me.
Johnny5
Been Around the Block
rafanomenon said:
Ah, they must be the same carbs that are on my bike. My bike is actually a 77 CB750K, but has a lot of the older style components on it. ie tank, ect. I say go with whatever works for you, but there are advantages to both. The new style carbs are easier to sync though.
What color are you going with on your bike?
rafanomenon
Been Around the Block
yeah.. there is another guy on the SOHC4 forums who swears by the F-model carbs, and actually got a little offended when I said I no longer wanted anything to do with them. :'( It really is all about what works for each individual setup. So far, so good...
I'm thinking about going gloss or satin black, with red accents. I want to give painting a try, so I plan on taking a weekend to do just that. There's going to be a lot of coating/wet-sanding going on! Eventually, I may have it professionally done. Then i'll probably go all red, just so I can name it the 'Red Rocket'. Pun intended on the dog boner ;D
I'm thinking about going gloss or satin black, with red accents. I want to give painting a try, so I plan on taking a weekend to do just that. There's going to be a lot of coating/wet-sanding going on! Eventually, I may have it professionally done. Then i'll probably go all red, just so I can name it the 'Red Rocket'. Pun intended on the dog boner ;D
rafanomenon
Been Around the Block
Disclaimer: This isn't pretty :-\
Got started denting on the actual tank a couple days ago. As stated, it dented unpredictably using the orange deadblow hammer. I didn't notice how imperfect it was until I stripped and sanded.
Overall, I'm happy with the general shape and location of the dents, minus the bastard crease towards the middle-bottom, especially on the right side of the tank. I didn't want to overdo it, so I stopped. I don't think this tank is totally scrap - just a little more bondo and shaping work than I had originally planned. The dent on the left side looks different in the pictures, but it's just the direction that the light is hitting the tank. The shape is pretty symmetrical on both sides.
Bondo and general shaping tomorrow and Friday. Paint this weekend!
Got started denting on the actual tank a couple days ago. As stated, it dented unpredictably using the orange deadblow hammer. I didn't notice how imperfect it was until I stripped and sanded.
Overall, I'm happy with the general shape and location of the dents, minus the bastard crease towards the middle-bottom, especially on the right side of the tank. I didn't want to overdo it, so I stopped. I don't think this tank is totally scrap - just a little more bondo and shaping work than I had originally planned. The dent on the left side looks different in the pictures, but it's just the direction that the light is hitting the tank. The shape is pretty symmetrical on both sides.
Bondo and general shaping tomorrow and Friday. Paint this weekend!
