Excessive timing chain slack?

[5twins]

What you guys might want to take a look at is an SR/XT/TT500 front guide and use that as a basis for a 650 one. The big problem with most of the 650 ones seems to be the rubber coming unbonded from the aluminum base. Apparently Yamaha never figured out a good enough way to bond the two materials together. The 500 guide uses a steel base and I've never heard of one falling apart like the 650 ones do.

http://www.ebay.com/itm/1977-YAMAHA...BLY-/111712047471?hash=item1a028e916f&vxp=mtr

My idea was to try and mount a 500 guide to an old 650 base. This could be the "cure" we've been seeking if a simple "home mechanic" mounting method could be devised. A big "plus" here is the cost. A new 500 guide is only about $25. The 500 uses the same cam chain as the later 447 650s so the guide is made to use with that size chain.

http://www.boats.net/parts/detail/yamaha/Y-583-12231-00-00.html

 

[Kgreenhaw]

That's not a bad idea! Maybe an adapter could be fabricated to bolt the xt guide to the xs engine... What were your ideas as far as mating the two guides?

 

[Brian902]

In another thread there were discussion of making other types of guides and 5Twin's 500 design was what I thought would work best. The center section runs on the rollers and IMHO would allow the guide to outlast any of the types that allow the side plates to gouge ruts into the guide material.

Easy for me to say, but cutting up a block of alluminum to bolt the 500 guide onto that would fit the mounting holes that exist in the cylinder block, doesn't seem like too big a task. This would allow using an un-modified XT500 guide and once the dimensions for the block were worked out, could easily be duplicated.

I don't thing there is enough material in a stock XS650 guide to allow mounting the XT500 guide without modifying both, which would be a waste of time. Modify the mounting block and using a stock XT500 guide just make more sense.

 

[TwoManyXS1Bs]

Snagged some pics of that 500 guide, scaled and overlaid with my XS1 guide pic. My best guess estimate for the length of the 500 guide is about 7 1/4" - 7 1/2", with the XS guide at 8". Wanted to see if any potential conflict with the mount tabs.

 

[Brian902]

Great pics TwoMany, looks like my idea of using un-mod xt guide is out the window.

Mounting taps on the xt guide are quite large, not much room at one end for mounting when you view the xs guide.

 

[TwoManyXS1Bs]

...Mounting taps on the xt guide are quite large, not much room at one end for mounting when you view the xs guide.

Yeah, this'll take some thought/planning.
Since I'm actually in this boat, I think I'll go ahead and buy one of the eBay offerings.


And sacrifice it to the God of Speed...

 

[5twins]

I happen to have one from an SR parts motor. I'll get some measurements and comparison pics (to the 650 guide) in the next day or so. Yes, the 500 guide is a little shorter, but I think we could work out how high or low to mount it (where to put the short end). Maybe split the difference, having it a little shorter on both the top and the bottom. As Brian noted, the 500 guide has a raised center, not edges (that quickly break off) like a 650 one.

I never did work out the mounting to an old 650 guide, but my idea was to cut it shorter so the 500 guide would slip on, and use a combination of short screws and JB Weld to attach it. A solid block of aluminum may be the ticket though. Besides shortening the 650 guide, some material would need to be skimmed off the front too. Laying the 500 guide right on top of a 650 base (rubber strip removed) makes it too thick.

 

[TwoManyXS1Bs]

I happen to have one from an SR parts motor. I'll get some measurements and comparison pics (to the 650 guide) in the next day or so.

Great, 5Twins! I went ahead and ordered an eBay salvage unit. $20 experiment.

Should be here before the snow flies.

... A solid block of aluminum may be the ticket though...

Agreed. That way, you have full control over those poorly-machined 6mm mount holes, and total mounting solidarity...

 

[Kgreenhaw]

cool guys! Excited to see what the results are. I would like to explore more on modding/making a front guide, but I can't get too distracted, I gotta finish my bike!

I have been researching materials and talking to my dad about making a solid plastic prototype. He's got a small CNC mill and has done a lot of prototyping stuff. It looks like there are viable options as far as using full plastic guides. The materials are expensive, but obtainable and there are a lot of automotive manufacturers using solid plastic timing chain guides.

 

[TwoManyXS1Bs]

My XT-500 front camchain slipper arrived. Did some quick comparison/alignment photos.
The XT-500 slipper is 10mm shorter. The short end has an orientation arrow pointing up.
So, the alignment/comparison pics maintain that orientation.
The mount lugs are too long, but don't seem to interfere with the XS1's mount bolt locations.
If/when I actually dive into this, I'll start a new thread. More pics in this album:

http://www.xs650.com/media/albums/2636/

 

[Brian902]

TooMany (beers, ha ha ha)

How about this idea; cut existing slide off XS aluminum mount and trim the aluminum block to fit between the XT mounting points like this, then epoxy the XT metal mount to the XS aluminum block. Also trimming XT mount points to length allowed of course.

Everything looks to thin for bolts. But not sure if epoxy would hold long term. Thinking the XT mounts fitted tight to the aluminum block would prevent up/down movement, pressure is pushing the XT mount into the XS aluminum block and the epoxy would hold it together.

Other idea would be to make an aluminum block that fit between the XT mounts but also was formed like the XS mount so it wrapped up around the steel frame of the XT mount preventing sideways movement.

Just some food for thought.

 

[TwoManyXS1Bs]

TooMany (beers, ha ha ha)

A Capital idea, Brian!

... make an aluminum block that fit between the XT mounts but also was formed like the XS mount so it wrapped up around the steel frame of the XT mount preventing sideways movement.

Just some food for thought.

Thanx, will chew on that awhile...

 

[angus67]

dog-eared
Man oh man. You guys are genius! Cant believe I didn't see this thread until now.
I think my 71 is revised with the xs2 parts, but just in case, this will be really handy when the parts don't fit together.
On the use of a grinding table to modify a new to old guide, If you change the angle 1* as shown, doesn't that also change the angle of the two 6mm bolts to hold it to the fin block? Causing a leak? and also a sure way to strip the threads out of the guide?

 

[TwoManyXS1Bs]

dog-eared
Cant believe I didn't see this thread until now.

Hey, Angus! Where ya been?
Yeah, this forum gets quite busy sometimes, hard to keep up.

I think my 71 is revised with the xs2 parts, but just in case, this will be really handy when the parts don't fit together.

The easy/quick tell for the XS2 parts is if your tensioner body is the 6-hole type "B" version.

On the use of a grinding table to modify a new to old guide, If you change the angle 1* as shown, doesn't that also change the angle of the two 6mm bolts to hold it to the fin block? Causing a leak? and also a sure way to strip the threads out of the guide?

Good question. I'd think 1 degree is about as far as I'd like to push those 6mm bolts. 1 degree is what we like to call "1 out of 60" when considering the sine of the angle. For example, a 0.600" bolt exposure, angled at 1 degree, will have its head displaced by 0.010". I think there's enough give in the cylinder bolt sleeves and guidebar threads to just about accomodate that...

 

[angus67]

Been building a shop, and a recent storm cut off internets for almost a week.

 

[TwoManyXS1Bs]

Thread update.
Here's JimD54's implementation of the Yamaha 500 front guide onto the XS650 front guide.

http://www.xs650.com/threads/cam-chain-guide-mod.51730/