lose the cam chains? '83 interceptor 750

I was tearing apart a spare engine in my shop a couple days ago, and had the idea of converting my '83 to gear drive cams. In my experience, the bean counters usually beat the engineers when it comes to changing something, so i was wondering if the gear cartridge from one of the vfr models would work... probably too much trouble... but then i found a set of gear drives from an '85 vf1000r, and they share the same bolt pattern as the chain tensioners for the vf750.

I also noticed the cams that were (supposedly) from the same bike had the exact same sprockets as my chain drive models... they look too narrow to me, what's the deal with that? i know the vf1000r gear drives are completely different than the vfr700/750, did they really just dump the cahins, and throw in gears with the rest staying the same?

Has anyone ever tried doing this before?

 

Seems to me if the gear ratio is even the slightest bit different than the chain would be it will always be out of time. Its a lot more math than I could figure out but that would be the main issue. Making sure the gears you put in match exactly to the chain you take out. Maybe you will come across a math wizard on here that can help you. If you get it wrong you will find out real quick. But good idea if you could figure it out. Good luck

 

I do know the gear teeth on the crank is different. The chain crank has two separate gears cut in them while the gear driven has one continuous gear. Could be it's easier to cut one instead of two and you don't need side clearance for the chains. I would bet they are the same number of teeth. You should try it. Put the gear cartridge in and then turn the engine over by hand several times to see where the cams line up. Would like to know myself. So let us know how it works.

 

How are you going to drive the cam gears? the 1000R has a teeth on the crank shaft to drive them.

 

I was thinking about simply running them on the crank sprockets... the spring loaded split gear will not function as intended though. it seems that the "gears" on the vf1000r may actually be the same part as the chain drive sprockets that are on the 750... or they were mis-labeled in the junkyard I got the gear drives from.

If the sprockets/gears are indeed different, or not compatible, I may be able to use the vf1000r cam gears on the 750 camshafts. The crank I haven't figured out an easy solution yet.

of course, this would only be easy if the deck height is the same, or at least extremely close. I'll check it out when i open the shop tuesday... or monday if i can't wait.

 

I'm a little tired, so i may be wrong. I think as long as the cams have double the teeth as the crank, the gears in between can have any number of teeth... provided there are two gears to keep things spinning the right direction. I hope i don't need to clean the garbage out of the machine shop.

 

okay, so i went to the shop today to drop off some stuff... the gear drive cartridges DO fit in the head. I will have to ream out two of the bolt holes a little bit for the locating dowels to fit, but that will be easy... ---- looks at the pile of trash on the milling machine ---- i wonder if i could do it by hand...

 

What crank do you plan to use? I cant see a VF750 crank with the sprocket teeth driving a cam gear drive, probably a different number of teeth on them (I do have one of each down the shed so will check when I get the chance). Similarly the cams with teeth for a chain are unlikely to work with the gear drive - as someone from the cb1100f website would say it would sound like 2 skeletons shagging on a tin roof.
Can you use a 1000R crank and cams? The cams from the US 85/86 models are a fair bit longer than the 84 1000R cams so maybe the 84 VF1000R cams will fit.

 

yeah, upon closer inspection, the sprockets don't jive well with the gears. the pitch is ever so slightly off.

The block will also require machining for the cartridges to fit between the cylinders, or maybe the raised portion on the bottom of the cartridges could be shaved off... what does that even do? catch oil for the lower bearing?

the 1kr cams are most likely too long, short, or fat, but it may be that easy. however, cam sprockets/gears have been known to have the exact same bolt centers. That may also solve the problem of the cartridge sitting too low to engage the cam gear properly.

I would be very interested in your comparison between the 750 and 1kr cranks. most importantly main bearing diameters, bearing centers, cramkshaft length, crank throw, rod length and wristpin diameter... basically, can i put it in the vf750 crankcase and use the 750 pistons with it...

thanks in advance for blowing an afternoon

 

I think the R" crank may have bigger mains. I read that some where. I believe the 1000F crank has the same mains as the 750. I've been trying to find out if the F crank will fit the 750 case. I believe it will (nice stroker kit) but don't have empirical prove of that. If the F crank fits (+rods) then you would just need pistons with the bore you want and the correct or close compression height.

 

yeah, main bearings are bigger. so are the wrist pins. and the cams... and the gears don't look like they will swap over without a fight. a fight they will get, i'm not giving up yet.

the gear drives only seem to have one problem going into the case. there is some sort of ridge that collects oil for the lower bearing on one side of the cartridge. it's either spend five minutes grinding that off, or three hours milling the water jacket. will grinding off that ridge and basically eliminating that pocket starve the lower bearing for oil? the top bearing has nothing like that, so why does the lower one need it? is it because it's a needle bearing and the top one is ball bearing? I have pictures, but i don't know how to upload tham here.

If i can get that gear drive to fit into the case, then i can get to the next problem i'm sure to encounter... the gear that is driven by the crank will most likely not reach, or be too far down. There's just the off chance that i'm lucky enough or honda is lazy enough to use something the same in that one way.

oh, and i figured out what that bolt on the front does... mine were missing, but i'm guessing it goes through the crankcase (at the bottom of the valley, under the carbs) to secure it from the bottom, right?

 

oh, one more thing. the cams i currently have in the bike did not come with sprockets, I had to use the ones from the old cams... this was years ago. I got them from a friend that used to race in the late 80s, he had some stuff left over. they were in a yoshi box, and said "for vf750/rs850". as far as i know, the rs850 uses gear drive cams, but are weapons grade unobtanium. are there any other gear drive cams that i could use the sprockets off of? it would probably save 4-5 hours each cam if i don't have to weld a new ring on and machine each tooth... i could definately live with turning down a gear and welding it on. I think they use 46 teeth on the cams, but that's judging from a 30 year old blueprint.

haven't figured out an easy way to do the crank yet.

upon further thinking, that blueprint must be too fuzzy to see properly. should it be 24 teeth on the crank, and 48 on the cams? that will be an even 15/7.5 degrees per tooth instead of some ungodly million decimal nightmare. the vf750 uses 23/46 for some reason, sonce i don't have a 1kr cam to verify, could someone that has one on hand look for me?

 

okay, the gear drives fit with a little machining to the case, and i mean a little. shaved a few milimetres near one of the main bearing bolts (cross fingers), and they fit. They even reach to the correct depth... lucky me i guess.

So i will most likely need to add some material to the crank, then machine teeth into it, not a problem... anyone know the module and pressure angle they use for the vf1kr cams? I'm still looking for something to use for the cam gears, but if i have to machine those too, i guess it's okay.

it seems both cranks use 23 teeth. strange, because hobbing is really the only way to cut gears for something of this scale production... only problem is, as far as i know, hobbing does not work when cutting prime numbers of teeth. if the cam gears end up having 46 teeth, i'm just gonna cut my own with 48 anyways. i don't have equipment precise enough to go much finer than half of a degree... 7.862086956521739130347etc. degrees is ridiculous when adding a tooth to the crank makes it an easy 7.5 degrees.

oh, since these gears (and the crank) seem to be cast iron, i'm guessing 1090 carbon steel will be okay to make these things with? i could harden them after machining. would mild steel be okay?

 

I don't think it will work. First off the chain cams all drive clockwise. The gear driven cams run anti-clockwise !
Thus the 750 cams will NOT work. The 1000 has a longer stroke than the 750, so the gear cartridges may be to tall to drive the cams ! Anything can be made to work, if you have the will, funds &/or engineering capability.

 

The longer stroke doesn't matter. The gear/teeth are on the main shaft and that's in the same on both engines and the deck height could be the same. Though the rotation difference I didn't know. Don't really want to run the cams backwards, now would we?

 

Just figgur a way to drop an '86/'87 700/750 engine into the VF, how about it ??

 

just spent about five minutes kicking my own ass. I didn't actually think about that.

I guess i could re-index the cams i have, or just use a set from a magna or sabre. i'll have to think about this.

 

too easy.



but it's an option.




maybe the whole 1kr motor.





maybe you have a spare?

 

+1 on the vfr 700/750 motor conversion. Not to mention you will gain about 20 hp

 

Naaaa to slow. Just need a 84 1000F or build a stroker motor using a 1000F crank/rods if you can find pistons that would work. Just a little hot rodding......