74 RD350 - Anything more than 2 strokes is a waste

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

In order to get my drive sprockets to line up with the supermoto rear wheel, some modification were in order. My initial measurements called for 15mm of offset to be corrected through an offset front sprocket and modifications to the sprocket carrier ring of the Excel hubs. I was able to knock out 9.5ish millimeters with a 3/8" offset sprocket from PBI. It's a 530 width that will be cut down to 520.

For the rear carrier ring modifications, I drew the stock geometry into Solidworks to have a model to work with. From there, I devised that I could buzz about 4mm from the width of the sprocket mounting flanges and 1mm from the back mating face. I did some crude FEA work to make sure things were still in the realm of safe.

I had a coworker print the modified carrier ring for me. There was a bit of warp in the printed part, but fortunately the business side of things was still usable. I got that mounted onto the wheel and did a final measurement with the straight edge to make sure I didn't miss with my measurements. Once the front sprocket is turned down the 1/8" (from the back face) things should be in alignment. I'm comfortable turning things over to a machinist for modification.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

Couple of updates to the build:
1. I got my 350 cylinders back after a bore/hone job to match the new Pro-X Banshee pistons. I might work on buttoning up the engine in the near future
2. I tested the function of my oil injection pump by running it on the bench. I'm waiting on the second set of seals (USPS lost the first package) to put that back together and get the right hand case cover back on the engine.
3. My 530 offset front sprocket was turned down to a 520 width.
4. The rear sprocket carrier pictured above was modified to bring front and rear sprockets in alignment
5. The rear hoop I ordered from Justin was a little too wide. I modified it and tacked it together, but something just didn't look right on the RD. I wanted a tail section that mimics the back of the gas tank, so I made it that way. Now I need to turn down some rod stock to fit inside the tubing where it meets the rear of the RD frame.
6. I ordered a bunch of fiberglass supplies. Life is about to get real itchy.

One last question - Do any of you guys have experience with the ballistic batteries on the bikes? With no electric start, I was thinking that the battery didn't need to be that big. I've poked around on the interwebs and it looks like guys are using the Ballistic EVO2 4 cell - 2.3A-h capacity.
http://www.ballisticparts.com/product_info.php?products_id=424

Any thoughts on whether or not this is enough juice to run the ignition, headlamp, and I plan to use LED's elsewhere.

 

[Tim]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

I have Shorai batteries and have had good luck with them. I did buy one Ballistic - the small one you're looking at to use on a kick-only project. I got it on eBay and it arrived dead. So just get one from somewhere reputable.

www.sparckmoto.com has a line of li-iron batteries - earthX.

The only reason you should need a battery at all is for the initial starting juice. If the charging system of the bike is working well, it will create more than enough power for the lights etc. Only problem is if you spend all your time idling around town. For my SR500 that has a PMA charging system, I'm going to be running a capacitor in place of a battery.

 

[Narb1989]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

This is a serious build. I too have built and mocked up parts for my 350f using Solidworks and a 3D printer. I think it makes a build more fun and rewarding when you use your talents and resources to make your own parts. From what I understand, cafe racers and the like were bikes modified and built by people using their own innovation. The same is done here with modern technology. Do you have an engineering degree of some sort? Well done.

Have you thought about using the plastic part to make a sand cast, and then make the part out of cast instead of having them machined?

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

I have Shorai batteries and have had good luck with them. I did buy one Ballistic - the small one you're looking at to use on a kick-only project. I got it on eBay and it arrived dead. So just get one from somewhere reputable.

www.sparckmoto.com has a line of li-iron batteries - earthX.

The only reason you should need a battery at all is for the initial starting juice. If the charging system of the bike is working well, it will create more than enough power for the lights etc. Only problem is if you spend all your time idling around town. For my SR500 that has a PMA charging system, I'm going to be running a capacitor in place of a battery.

Thanks for the reply. I was hoping to hide the battery in the area between the frame rails under the rear of the tank. The size of the Ballistic battery was why was drawn to it. Those batteries from Sparckmoto look good from the standpoint of being able to use any charger along with the battery management system built in.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

This is a serious build. I too have built and mocked up parts for my 350f using Solidworks and a 3D printer. I think it makes a build more fun and rewarding when you use your talents and resources to make your own parts. From what I understand, cafe racers and the like were bikes modified and built by people using their own innovation. The same is done here with modern technology. Do you have an engineering degree of some sort? Well done.

Have you thought about using the plastic part to make a sand cast, and then make the part out of cast instead of having them machined?

Thank you for the compliments. I have a pair of Mechanical Engineering degrees, which help with eye-balling some sizes, dimensions, and the occasional stress calculation like I did for a previous iteration of my rear suspension. The funny thing is, in my mechanical engineering job, I don't get to do much design work. It's a lot of project management and organizational problem solving. When I get a chance to create parts or systems in Solidworks or even with the basic fabrication skills that I have, I jump on it. It is incredibly rewarding to using your hands to manifest a vision in your head.

No plans to do any sandcasting because these are relatively simple parts. They're all also completely one-offs with no use outside of my build. I'm having a number of these flat pieces laser cut currently, so I'm hoping to have an update for you guys on how those came out.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

I have a quick question on assembly of the oil pump to the case cover. I've looked at some microfiche of the oil pump assemblies and I'm seeing a part called "worm gear outer" which looks like a bushing. I don't have anything like that. The case has a raised boss that extends outward and appears to support the pump work gear shaft. There isn't any play in the shaft, so I'm guessing I have it right. Was that bushing an update to later models?

 

[jpmobius]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

There is no update, all 73-75 RD250's and 350's are the same in this regard AFAIK. There is a steel boss pressed into the cover that the worm/shaft rides in which is a separate part that assembles from other side of the cover. The boss also precisely located the oil pump. If the pump is installed, you cannot see it. Usually it is pressed into the cover, but often it is just a tight slip fit and comes out with the shaft. As long as it fits with no play in the cover it will be fine as the seal is inboard of the bushing. Take a closer look, you should see it is a separate part, though certainly it would be possible to make it integral. Note that the assembly is counter intuitive in that the clip installs first against the seal. The washer does not go under it as might be expected. The order of the parts is as you have it in your pics.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

There is no update, all 73-75 RD250's and 350's are the same in this regard AFAIK. There is a steel boss pressed into the cover that the worm/shaft rides in which is a separate part that assembles from other side of the cover. The boss also precisely located the oil pump. If the pump is installed, you cannot see it. Usually it is pressed into the cover, but often it is just a tight slip fit and comes out with the shaft. As long as it fits with no play in the cover it will be fine as the seal is inboard of the bushing. Take a closer look, you should see it is a separate part, though certainly it would be possible to make it integral. Note that the assembly is counter intuitive in that the clip installs first against the seal. The washer does not go under it as might be expected. The order of the parts is as you have it in your pics.

I pulled the pump off the cover to check. The bushing stuck in the cover so well that I had just thought it was part of the cover rather than a separate piece. It's all good in the hood. Thanks for the reply.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

I ended up having a pretty solid weekend. I sent the woman home to see her parents for the weekend and spent a lot of time in the garage.

I keep having these horrible ideas of building my own pipe(s) (Ya, I'm thinking 2 into 1...) rather than just buying a set of DG's and moving on with my life. So I made a degree wheel and mapped out my port timing. Transferred the port/cylinder geometry onto some paper as well and got all of my specs to enter into the Build and Click pipe design software.

I cleaned up some of the stock chrome pieces that I won't be carrying over to my build. They're posted up for sale in the "selling" threads here http://www.dotheton.com/forum/index.php?topic=64221.0

After mapping the ports, I finished putting the top end together. I had installed a new crank from Vito's when I was building the bottom end/trans - I found it interesting that the Yamaha wrist pin bearings didn't fit the con rod ID from the Vito's crank. I used the wrist pin bearings that were supplied with the crank. *If anyone needs genuine Yamaha wrist pin bearings, PM me - I'll ship them for what I paid for them from Economy Cycle*

I finished off the engine in the house (remember that part about the woman leaving for the weekend?) I wanted to get everything up to room temp before torquing the cylinder heads down to 15lb-ft.

Take a look at the 4th pic below - I used a set of Banshee pistons and modified the intake skirt. In the ring pack, there were these 2 weird rings that almost look like the oil ring separator in a 4st piston. Does anyone know what these are and should I have installed them?

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

So I'm planning and preparing to get itchy. I have all I need to get started with fiberglass except a design. So I took a crack at laying out a silhouette in cardboard today to get a feel for what I'm after. I want the rear cowel section to mimic or flow with the lines of the stock RD tank. The rear will also house an oil tank.

I mocked up some cardboard, but didn't really like the shape of what I came up with. It's much easier to mock things up in Solidworks, so I took a picture and loaded it into the sketch background (this is a great feature). I've been doing this for a lot of brackets that start as cardboard templates. On each pieces, I lay a scale on the cardboard, then resize the photo in Solidworks until the scale on the cardboard matches a scaled line in Solidworks.

I couldn't fill the sketch outlines in Solidworks, so I took it to Photoshop. The picture below is the extent of my capability in Photoshop. What do you guys think about these lines?

 

[jpmobius]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

Those funky bands go underneath the lower rings. I use them, but many people claim to leave them out and see no difference. I note that they are not universal, but do use them when provided by the manufacturer. Seems like not using them would leave a void behind the ring if the ring was designed to have it there, but don't see how that would do any harm. Always seem to get good results using them, so have no ambition to experiment leaving them out. Don't forget to check those ring end gaps!

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

Those funky bands go underneath the lower rings. I use them, but many people claim to leave them out and see no difference. I note that they are not universal, but do use them when provided by the manufacturer. Seems like not using them would leave a void behind the ring if the ring was designed to have it there, but don't see how that would do any harm. Always seem to get good results using them, so have no ambition to experiment leaving them out. Don't forget to check those ring end gaps!

Thanks Mobius. I ordered a Pro-X Banshee piston kit from a dealership in Ohio. I found a pretty good deal on the top end through some web searching. When I got the parts, it seemed to be a bit of a hodge-podge of sorts. Pro-X piston boxes, some other kind of rings, wrist pins wrapped in paper with Japanese writing, and the circlips were in small plastic bags. It didn't seem like a "set"
I'll give Pro-X a call today to ask about that spring steel ring that goes under the lower ring. I've already torqued my cyl head bolts and don't want to waste that set of copper head gaskets if I don't have to.
If I remember correctly, there wasn't much room between the lower ring and the groove. I can't imagine that there was room to place that other ring under the lower ring. The lower ring was noticeably thicker than the upper ring and the piston ring grooves were cut accordingly - i.e. the lower ring wouldn't fit in the upper groove.

 

[jpmobius]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

All the Pro-X pistons I have seen come like you describe - seemingly parts from many suppliers. Never had an issue. The upper ring is tapered like a wedge so you can't swap them. Stock RD250 and 350 heads are notoriously hard (impossible?) to seal. The gaskets can be used indefinitely if you anneal them. Plenty of U-tube on how to do it - you only need a propane torch. If you have unmodified heads, they can be made to work, but you may have trouble even if you only add chambers. You can try things the way you have them since you have already put it together, but if it leaks, try the following. Take the heads off and lap them on a piece of glass with some #400 wet sandpaper. Rd heads are very bendy and likely very not flat. Anneal your gaskets. Give them a good coat of spray Copper Coat on both sides and let dry. Them give them another light spray and assemble. It is ULTRA CRITICAL to NOT over torque the head bolts!! I think it is 16 lb-ft. but look it up. The problem is that the bolt pattern is entirely outboard of the gasket, and over torquing the bolts bends the head down at the bolts over the gasket causing it to bow up between the bolts. When you lap the heads you will likely see this for yourself. Creep up carefully on the final torque and re-torque after 5 minutes of run time, after coming up to full temperature and cooling down, and after your first short ride and your second. Likely will hold indefineately after that if your engine is mostly stock.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

Great advice Mobius. I did lap the cyl heads on plate glass before installing, but didn't know about annealing copper head gaskets. I did take 4 steps of criss-cross tightening. I think the right thing to do here is pull the heads and cylinders. I'll be able to install the support ring on the piston and anneal the head gaskets. Hopefully those base gaskets won't leak after trying to reuse them...

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

Took the time to pull the cylinder heads, anneal the head gaskets, and install the lower ring back up ring. I also was able to measure my squish using solder placed facing each of the 4 cylinder bolts per cylinder. The heads I have have been milled to remove the step. This put me at a squish height of 0.039"-0.040" squish. From the research and reading I've done, this seems to be the spot where performance and reliability meet and is safe to run on pump gas. If needed, I could always switch from the 0.020" base gasket to a 0.016" if I wanted to tighten that up some.

 

[jpmobius]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

I never re-use the base gaskets, in fact I feel like most people underestimate the importance of a perfect seal at the cylinder base. I have had leaky joints on some cases I think a result of over torquing the heads. Short of milling the cylinder base surface flat I use Yamabond or 3-bond on one side of the stock thickness gaskets and Loctite 518 or similar on the other so I can get it back apart a bit more easily and have high confidence in the seal. Definitely overkill if your case is perfect, but it can't hurt. I've resurrected some pretty beat up RD motors! Be prepared for trouble sealing the heads. I think your squish is fine, but would not go skinnier without pinning the heads. I mill off the top of the cylinders to remove the step that located the head gasket so I can use RD400 gaskets. This is a tremendous improvement in sealing reliability but the gasket is thinner so you would have to put some focus on your squish clearance if you find you need this solution. I always use the Copper Coat spray and torquing regimen described previously. Milling the cylinders and cutting a grove for an o-ring in the head is a 100% solution, but you have to re-machine the combustion chamber to get your squish clearance back. Alternatively you can leave the cylinders alone and cut a matching step in the head along with the o-ring groove. This is actually better because the step centers up the head and the o-ring makes a totally reliable seal. Get the squish and combustion chamber volume where you where you want it, and you have a total solution!

 

[clem]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

As far as the battery goes, don't use the 4 cell. It's not enough load for the system(if it is an MZB). I bought the 8 cell ballistic and it seems to do fine. With those type of batteries you cannot over charge them beyond 14.4v or they will get damaged. I learned that in my RC experience when everything went to LiPo batteries.

 

[imtyson]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

love the tires and the geometry of the bike.

 

[jchek779]

Re: 74 RD250...is now a 350 - Anything more than 2 strokes is a waste

I didn't get as far as I wanted this weekend, but progress is progress.

One of my co-workers was sent to Germany for the week, so I told him I'd babysit his benchtop lathe and mille. I was able to crank out a set of frame slugs to mate my frame to tail hoop and I came up with an idea for a plug to block off the tach drive opening.

I turned a 5/8" piece of aluminum with an O-ring groove and a 1/2" shoulder. The shoulder fit into a 1/2" hole in some 3/32 aluminum plate I had kicking around. Melt the 2 together and grind to shape. Don't stare too long at the TIG weld...you're eyes will be damaged by how ugly the bead looks. Some days I've got it. Yesterday I just didn't.

I was going to permanently affix the seat hoop to the frame, but I ran out of shielding gas. So i turned the lights off and left.