main bearing lip

[two-stroke-brit]

just got the main brgs from paul miller and they have a lip in the ineer race.




not seen this before ??.
is this normal.
thanks mark.

[Suzsmokeyallan]

Its definately got to be there if not the pure oil flow from the main bearings cant cross over to the lower ends.
The crank has an oil guide plate on the same side of the crank that fits over that ring. Then its guided to a hole in the same plate into the hollow lower end pin where it is then guided up to the big end bearing through another cross drilled hole in the big end pin.
Thats how the big end pins get their oil supply from the main bearings.
Stop that flow of oil in any way on the CCI system and you can kiss the lower ends goodbye.

[tz375]

Oh. And that would be another good reason to not try premix on a street GT750

[H2RICK]

And that would be another good reason to not try premix on a street GT750

What?? Do you mean Suzi strokers don't have a low rent intake-tract-only injection system like the brand y strokers ?? Well, I'm shocked.....

[tz375]

Afraid so Rick. Brand S are famed for their more complex crank oil arrangements which don't work as well at high outputs, and have to be extensively modified to work on a race motor.

They are fine on teh street as long as a big end oilway doesn't clog.

[Suzsmokeyallan]

Richard ive never seen a big end oil path clog on a CCI motor. What can and does sometime happen from years of use is the spigot on the oil guide plate can shear off from fatique causing the oil path to the big end to be rendered useless.
Premix works well as long as the motor is designed for that system and since the majority of two stroke engines sold were for street use, a metered system such as CCI was the best way to do it.
I'm not sure how you would classify rpms for racing but for most applications upwards of 250CCs in engine size, id say at or over 8,000 rpms on a regular basis is in that sort of league.
The smaller road bikes such as the GT250X7 was a buzz bomb and worked well up in those rpm ranges with longevity to the parts that the KHs and RDs could not match.
As you well know those bikes carried a CCI system and most X7 owners who race or ride their bikes really hard will tell you it works great with many miles on their internal bearings and related parts.

[tz375]

Allan, That was in interesting reply to a couple of tongue in cheek posts.

I wasn't attacking Suzuki's unusual design for street motors (much), but it is different to most other two strokes and that doesn't make it any better.

Just in case you might have been misled by by last post, I am a big fan of oil injection for street bikes and don't favor pre-mix on the street.

But for a race bike, the Suzuki designs are harder to convert to pre-mix and less reliable under race conditions. That doesn't make them bad for a street bike, just unnecessarily complicated and expensive compared to other simpler systems which work just as well on the street or on the track.

Racing is not about 250 up at more than 8k, it can be 50cc twins racers at 18,000, or 125cc four cylinders or a 250 MX bike rarely seeing 8k. It's about loads and sustained heat soak etc rather than just engine size or rpms.

I used a simple example of blockage, but feel free to insert, failed check valve or oil pump problem etc. Yes I know they are very reliable, but IF there's any malfunction, there is no escape path. The system is unforgiving, or if you prefer, has no backup plan.

It's like most things in life, it's a compromise. Suzuki decided that the extra cost and complexity was worthwhile. Who knew back in 1970, what was best?

But to your point, how did Suzuki design say the X7 250 or say the RGV250. The RGV is more like a brand Y system leading us to believe that they realized that maybe it wasn't the best design and maybe a different compromise was more appropriate.

But for a street motors, it's not an issue either way.

[Suzsmokeyallan]

Richard i think we will agree to agree as well as disagree on many things. I cant answer all the effects about CCI or premix because theres too much pros and cons in this area.
So i have to go with what ive seen firsthand over the last 36 years or so dealing with all manner of two strokes.

[oldjapanesebikes]

not seen this before ??.
is this normal.
thanks mark.

And the short answer to your question Mark, is 'yes' for your engine

[pjmcburney]

But to your point, how did Suzuki design say the X7 250 or say the RGV250. The RGV is more like a brand Y system leading us to believe that they realized that maybe it wasn't the best design and maybe a different compromise was more appropriate.

But for a street motors, it's not an issue either way.

Richard,

As a fellow brand Y owner, whilst the system employed on these bikes seems simple, it also seems rather effective (as you alluded).
It does make for an easier change to premix, but why would you bother?

I spotted a heavily modified RZ350 at the Storey Bridge Concours last year, and the owner proudly displayed that he'd converted the bike to run on premix. Why you'd willingly do that, especially on a street bike is beyond me.
I can only conclude that the guy was either a tool, or he thought he knew what he was on about by listening to some other tool...

Not only did Suzuki use the same system on RGV's, they used it to great effect on RG's as well.
My RG500 only has 'injection' ports in the carbs. There are no ports or oilways in or into the crankcases.

RG's are perhaps a bit more fragile than say a GT750, but treated with respect an RG500 engine can last as long as a GT, and even when they do let go, it's rarely because the mains or the big-ends have packed it in.

To get back on subject, I concur that disconnecting the oil injection system (regardless of its design) on a street bike is a waste of time and a propensity for disaster.

I actually want to fit an injection system of some kind to my KTM - any ideas?
Electric pump, TPS controlled?


Cheers
Paul

[tz375]

The whole premix works for racers so it must be better than injection BS does still rear its ugly head from time to time.

Sounds like we all agree violently that it's a waste of time on a street bike.

As to whether it's a better system, it seems to me that all modern motors as well as the last Suzuki 2 strokes are use the simplest method possible. Modern Hi Po sleds making 180 HP from a 800cc twin just squirt the stuff into the intake manifold.

So my take ways from that was that teh GT system was good but the simpler systems are better

[Suzukidave]

http://www.3cyl.com/mraxl/gt/manuals/gt750man/sr43.htm

[tz375]

Thanks Dave. I need to bookmark that. I can never find it when I'm looking up oil pump rates etc.

[Suzukidave]

Richard , you might just save his whole site with all the great info there http://www.3cyl.com/

[tz375]

Done!. Thanks again.