Vintage Privateer Smoker (RD350 Race Bike)
- Thread starter TurdFurguson
- Start date
Re: First Vintage Race Inspired Smoker
I have replaced the two long front (8mm dia) bolts with 4 (12mm I think) bolts. It is very easy to drill and tap the engine case to accept the bolts. I have done several bikes like this, one with a zillion miles on it and have seen no stress or fatigue issues (not that I expected any, just verifying). Looks a lot nicer as well to my eye, and of course a bit easier to put them in. Also, the lower rear bolt can be shorter if you eliminate the passenger peg mount and spacer.
I have replaced the two long front (8mm dia) bolts with 4 (12mm I think) bolts. It is very easy to drill and tap the engine case to accept the bolts. I have done several bikes like this, one with a zillion miles on it and have seen no stress or fatigue issues (not that I expected any, just verifying). Looks a lot nicer as well to my eye, and of course a bit easier to put them in. Also, the lower rear bolt can be shorter if you eliminate the passenger peg mount and spacer.
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Re: First Vintage Race Inspired Smoker
I'll ponder over the drilling and tapping. Hadn't thought of that. I'm using part of the passenger peg mount as some of the rear brake pieces are attached and I left the brake mechanism in tact. I think the way it sits now that hole is still there for use with the longer bolt.
Got some time with mothgils again tonight, got most of the frame cleaned up and got the front pinch bolt bracket cut and on the tube. Looks kinda like a bunny with the gauge mount on there as well.
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I'll ponder over the drilling and tapping. Hadn't thought of that. I'm using part of the passenger peg mount as some of the rear brake pieces are attached and I left the brake mechanism in tact. I think the way it sits now that hole is still there for use with the longer bolt.
Got some time with mothgils again tonight, got most of the frame cleaned up and got the front pinch bolt bracket cut and on the tube. Looks kinda like a bunny with the gauge mount on there as well.
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Re: First Vintage Race Inspired Smoker
Also, is that another motor mount on the top of the motor to cross brace on the frame? If so, my frame had that cut off already..
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jpmobius said:
Also, is that another motor mount on the top of the motor to cross brace on the frame? If so, my frame had that cut off already..
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Re: First Vintage Race Inspired Smoker
Ok, that is for sure a removeable engine mount back there. So, question is how important is that guy? Do I need to fab up a new mount back there or should I be good just leaving it open? With how its designed, It really doesn't seem like its that important.
Ok, that is for sure a removeable engine mount back there. So, question is how important is that guy? Do I need to fab up a new mount back there or should I be good just leaving it open? With how its designed, It really doesn't seem like its that important.
Re: First Vintage Race Inspired Smoker
Yes, that is another mount. Can't imagine why it would be removed, but I would replace it. No doubt the bike will be safe without it, but that mount when bolted up to the engine makes that part of the frame a lot more rigid. Since that is the part of the frame that controls where the swing arm "aims", keeping that part of the frame stiff is important. For the record, I've seen RD frames fatigue crack just above the upper front mount, so probably a good idea to keep all the mounts! The mount is simple enough, but will be a nuisance to fab up. It uses two triangular plates, one on each side of the large boss on the top case half, a 10mm bolt through that and two 8mm bolts at the frame. The stock plates are steel, I have replaced them with much thicker aluminum plates and longer bolts on a couple of bikes. The frame has a straight tube across it with two small flat brackets that hold two tubes the same length as the width as the case boss. I'll look to see if I have a better pic, but the one above is not too bad if you click on it and blow it up.
edit: found these pics. Also realized that the lower mount for the right side cover is attached to the cross tube.
Yes, that is another mount. Can't imagine why it would be removed, but I would replace it. No doubt the bike will be safe without it, but that mount when bolted up to the engine makes that part of the frame a lot more rigid. Since that is the part of the frame that controls where the swing arm "aims", keeping that part of the frame stiff is important. For the record, I've seen RD frames fatigue crack just above the upper front mount, so probably a good idea to keep all the mounts! The mount is simple enough, but will be a nuisance to fab up. It uses two triangular plates, one on each side of the large boss on the top case half, a 10mm bolt through that and two 8mm bolts at the frame. The stock plates are steel, I have replaced them with much thicker aluminum plates and longer bolts on a couple of bikes. The frame has a straight tube across it with two small flat brackets that hold two tubes the same length as the width as the case boss. I'll look to see if I have a better pic, but the one above is not too bad if you click on it and blow it up.
edit: found these pics. Also realized that the lower mount for the right side cover is attached to the cross tube.
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Re: First Vintage Race Inspired Smoker
The cross tube appears to be there, but the mount appears to have been ground off. On race bikes with rubber front mounts, we leave that one off to save it tearing the mount and tacho drive out of the cases. On a solid mount engine it would be useful but probably not 100% necessary as long as the frame cross tube is there.
The cross tube appears to be there, but the mount appears to have been ground off. On race bikes with rubber front mounts, we leave that one off to save it tearing the mount and tacho drive out of the cases. On a solid mount engine it would be useful but probably not 100% necessary as long as the frame cross tube is there.
Re: First Vintage Race Inspired Smoker
Yikes! Never seen that. I guess if you were ok with the chassis without that mount, its use of the engine as a stressed element is pretty negligible. Goes right along with what I have long said: It can work great for 100,000 miles on the street, but you take it to one race . . .
teazer said:
Yikes! Never seen that. I guess if you were ok with the chassis without that mount, its use of the engine as a stressed element is pretty negligible. Goes right along with what I have long said: It can work great for 100,000 miles on the street, but you take it to one race . . .
Re: First Vintage Race Inspired Smoker
yeah, the cross tube is there, they had just cut the mount off. The other mounts are standard solid mounts, so i'll see if we cant come up with something to replace it. Maybe something smaller, if it turns into a mess maybe fuck it..
teazer said:
yeah, the cross tube is there, they had just cut the mount off. The other mounts are standard solid mounts, so i'll see if we cant come up with something to replace it. Maybe something smaller, if it turns into a mess maybe fuck it..
CarbsAndCylinders
Careful With That Axe Eugene
Re: First Vintage Race Inspired Smoker
I read a comment somewhere which said that the RD engine is too lightly built to use as a stressed member, not sure if that is correct but the engine would have to add at least some rigidity. One time guys would replace engine mount bolts with ones that fit very tight in their bores in order to stress the engine. I always thought that the RD had a pretty good frame for a 70's bike, do any people add gusseting to it?
I read a comment somewhere which said that the RD engine is too lightly built to use as a stressed member, not sure if that is correct but the engine would have to add at least some rigidity. One time guys would replace engine mount bolts with ones that fit very tight in their bores in order to stress the engine. I always thought that the RD had a pretty good frame for a 70's bike, do any people add gusseting to it?
sav0r
Coast to Coast
Re: First Vintage Race Inspired Smoker
If an RD engine adds rigidity it certainly isn't much. The bolt holes are all so sloppy you'll never get any legitment degree of support. If one was to fit up new motor mounts and use tapered pins rather than bolts you might actually be able to lean on the engine a bit. Whether it's capable of withstanding the forces is another story though.
That said, lots of guys forgo the upper rear mount on RD's without any issues. I like to use it though.
If an RD engine adds rigidity it certainly isn't much. The bolt holes are all so sloppy you'll never get any legitment degree of support. If one was to fit up new motor mounts and use tapered pins rather than bolts you might actually be able to lean on the engine a bit. Whether it's capable of withstanding the forces is another story though.
That said, lots of guys forgo the upper rear mount on RD's without any issues. I like to use it though.
CarbsAndCylinders
Careful With That Axe Eugene
Re: First Vintage Race Inspired Smoker
I should have said that I meant 70's bikes in general, not the RD specifically.
That tapered pin idea sounds pretty neat.
CarbsAndCylinders said:
I should have said that I meant 70's bikes in general, not the RD specifically.
That tapered pin idea sounds pretty neat.
Re: First Vintage Race Inspired Smoker
I've always felt that there was no downside and potentially some good value in clamping a solid mount engine very tightly into the chassis. While the original design may not have been as a stressed member, there is no doubt that pretty much any engine is a mighty stiff lump and if the chassis surrounding it fits well, solidly bolting it all together can only serve to make a more solid and stiff combination. So I always take at least some time to make sure the frame to engine fitment is good, and make all the bolted connections solid and tight. I think ream fitting the connections or assembling with tapered pins etc. would be fine, but superfluous. I think properly sized bolts with sufficient clamping pressure will keep the components from shuffling against each other under most conditions so going crazy to address shear between the parts is not needed. That's one of the reasons I like the 4 separate bolts on the front of the RD. You can get a lot of clamping pressure at the connections without clamping the case itself. The front mounts on the Rd are sort of like ears hanging off the front of the case with a fairly small web between them, and I don't like the notion of distorting the case with a lot of clamping pressure between them. The two rear mounts clamp a more solid and continuous section though there is no reason you couldn't drill and tap the lower mount just like the front - certainly an option if you are missing the long bolt! In any event, when I do it, I mount the engine in the frame, and drill and tap one of the mounts and bolt it up tight. Drilled together, the fit is excellent despite doing it by hand. Then I do the opposite side, and bolt it up. Then remove the bottom bolt and drill and tap the bottom. The result is a pretty darn good fit and a far cry from the yes, very sloppy factory fit. At the end it is all very likely not that critical, but the investment to simply do a good and careful job of the assembly is very small regardless of the fasteners or any modifications.
I've always felt that there was no downside and potentially some good value in clamping a solid mount engine very tightly into the chassis. While the original design may not have been as a stressed member, there is no doubt that pretty much any engine is a mighty stiff lump and if the chassis surrounding it fits well, solidly bolting it all together can only serve to make a more solid and stiff combination. So I always take at least some time to make sure the frame to engine fitment is good, and make all the bolted connections solid and tight. I think ream fitting the connections or assembling with tapered pins etc. would be fine, but superfluous. I think properly sized bolts with sufficient clamping pressure will keep the components from shuffling against each other under most conditions so going crazy to address shear between the parts is not needed. That's one of the reasons I like the 4 separate bolts on the front of the RD. You can get a lot of clamping pressure at the connections without clamping the case itself. The front mounts on the Rd are sort of like ears hanging off the front of the case with a fairly small web between them, and I don't like the notion of distorting the case with a lot of clamping pressure between them. The two rear mounts clamp a more solid and continuous section though there is no reason you couldn't drill and tap the lower mount just like the front - certainly an option if you are missing the long bolt! In any event, when I do it, I mount the engine in the frame, and drill and tap one of the mounts and bolt it up tight. Drilled together, the fit is excellent despite doing it by hand. Then I do the opposite side, and bolt it up. Then remove the bottom bolt and drill and tap the bottom. The result is a pretty darn good fit and a far cry from the yes, very sloppy factory fit. At the end it is all very likely not that critical, but the investment to simply do a good and careful job of the assembly is very small regardless of the fasteners or any modifications.
sav0r
Coast to Coast
Re: First Vintage Race Inspired Smoker
I guess my thinking is that if somebody truly wants to make th engine a stressed member it would be nice if the slop around the shear points could be as close to zero as possible. In all the frame testing I have ever done, most of which was on tube frame formula cars with stressed engines (some of which was on carbon tubs), the first degree of movement experienced was almost always related back to fasteners. This was almost always aided through three separate mechanisms. Firstly, large multi-point mating surfaces almost always needed shimmed to achieve even loading across the surface. It was common to see engine block mounts broken off when they were improperly / not shimmed. Secondly, sloppy bolt holes can allow for movement in extreme conditions and due to the friction between mating surfaces can actually leave the chassis in a preloaded state. That was exemplified in many chassis where corner weights would fluctuate between sessions and was actually remedied by loosening certain bolts and tensioning them on the scale pad. And finally, the use of tapered pins and or tapered mounting fixtures completely removed all of the slop at the fastening points. After this it was down to chassis and engine design to reduce flexure.
All of that in mind, this almost certainly has no effect on the ordinary rider of a 40 year old motorcycle and I completely agree that simply assembly things nicely will be more than enough. That's why my RD uses the stock fasteners.
jpmobius said:
I guess my thinking is that if somebody truly wants to make th engine a stressed member it would be nice if the slop around the shear points could be as close to zero as possible. In all the frame testing I have ever done, most of which was on tube frame formula cars with stressed engines (some of which was on carbon tubs), the first degree of movement experienced was almost always related back to fasteners. This was almost always aided through three separate mechanisms. Firstly, large multi-point mating surfaces almost always needed shimmed to achieve even loading across the surface. It was common to see engine block mounts broken off when they were improperly / not shimmed. Secondly, sloppy bolt holes can allow for movement in extreme conditions and due to the friction between mating surfaces can actually leave the chassis in a preloaded state. That was exemplified in many chassis where corner weights would fluctuate between sessions and was actually remedied by loosening certain bolts and tensioning them on the scale pad. And finally, the use of tapered pins and or tapered mounting fixtures completely removed all of the slop at the fastening points. After this it was down to chassis and engine design to reduce flexure.
All of that in mind, this almost certainly has no effect on the ordinary rider of a 40 year old motorcycle and I completely agree that simply assembly things nicely will be more than enough. That's why my RD uses the stock fasteners.
Re: First Vintage Race Inspired Smoker
Agree on all points! Probably why a little bike like an RD behaves as well as it does. Small and light means pretty low loads. If you compare the forces involved (at least compared to any race car) with the comparatively beefy scale of fasteners, frame tubing and physical size of the engine case I think it is pretty hard to get into trouble. I'd be the last person to promote even the "improved" bolt up I described as motion free given sufficient load, but reckon the loads both small enough to maintain no motion between the parts, and of rather little significance if there is! And while I may like the "bolt mod" and have used it on one of my own bikes and others, I have all the stock bolts on my own all stock RD and it drives like a dream!
Sav0r said:
Agree on all points! Probably why a little bike like an RD behaves as well as it does. Small and light means pretty low loads. If you compare the forces involved (at least compared to any race car) with the comparatively beefy scale of fasteners, frame tubing and physical size of the engine case I think it is pretty hard to get into trouble. I'd be the last person to promote even the "improved" bolt up I described as motion free given sufficient load, but reckon the loads both small enough to maintain no motion between the parts, and of rather little significance if there is! And while I may like the "bolt mod" and have used it on one of my own bikes and others, I have all the stock bolts on my own all stock RD and it drives like a dream!
Re: First Vintage Race Inspired Smoker
Kinda crazy the different philosophies that people have. Should be solid as possible, might be good on street but without begin solid would rip apart in a race. Vs. For race bikes we use rubber mounts and remove things so they dont rip apart.
I hope to get this bike out in some track days and AHRMA at some point, but it'll mostly be a show/city queen. I'm going to try and get a rear mount fabed up but worst case i wont lose sleep if it doesn't work out. Worst case I crack the frame, throw it in the trash and take another out of the attic.
jpmobius said:
teazer said:
Kinda crazy the different philosophies that people have. Should be solid as possible, might be good on street but without begin solid would rip apart in a race. Vs. For race bikes we use rubber mounts and remove things so they dont rip apart.
I hope to get this bike out in some track days and AHRMA at some point, but it'll mostly be a show/city queen. I'm going to try and get a rear mount fabed up but worst case i wont lose sleep if it doesn't work out. Worst case I crack the frame, throw it in the trash and take another out of the attic.
Re: First Vintage Race Inspired Smoker
More pieces fused to the frame. I think one more day of welding and it'll be ready for powder
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More pieces fused to the frame. I think one more day of welding and it'll be ready for powder
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Re: First Vintage Race Inspired Smoker
Had to get the tail light set in the seat before we could finalize the frame. No idea what I'm doing but I think this will clean up well in the end.
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Had to get the tail light set in the seat before we could finalize the frame. No idea what I'm doing but I think this will clean up well in the end.
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Re: First Vintage Race Inspired Smoker
big stuff ready to go out for blasting and powder, a little behind schedule but I still think it's doable as long as I keep working on things while its out.
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big stuff ready to go out for blasting and powder, a little behind schedule but I still think it's doable as long as I keep working on things while its out.
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