Extended drains on a shared sump?

[Eiron]

I'm the new owner of an '82 Honda C70 Passport moped-style motorbike. I bought it with 10,800 mi & it now has 12,300 on it. The engine is an air-cooled 72cc 4 stroke & shares 0.7L of oil with the semi-auto 3 speed tranny & centifugal clutch. The primary oil recommendation is 10W-40 with 20W-40/20W-50 as alternatives & 10W-30 allowed only up to 90°F max. The changes only replace 0.6L of oil, or about 85%. The change intervals are spaced at 1,250 mi or one year. It only has an oil screen, which it says to clean every 5k mi.

I've just finished the Auto-Rx clean phase using Delvac 1300 Super 15W-40 for about 1,100 mi & I'm now in the rinse phase with it. I forgot to clean the oil screen when I changed the oil, so I'll do that when I'm done with the rinse oil.

I'm using this as a commuter vehicle & I'm putting about 1k mi/mo on it. I plan on filling with M1 5W-40 when this A-Rx rinse is done. I'd like to extend the OCIs out as much as possible, but I'm not familiar with a shared sump like this & don't know how to go about figgerin OCIs. Can I do a simple X-factor when using this syn? (eg, 3X dino)

Thanks for the help!

 

[Blake Sobiloff]

Without a true oil filter you're probably doomed to short OCIs; your insoluables and wear metals will climb rapidly without an effective filtration device in place. If these aren't removed on a regular basis by frequent oil changes you'll suffer from abrasive wear throughout the engine and transmission.

 

[penzdude]

agreed. if the change intervals are spec'd at 1,250 mi and you are planning 1k a month, i'd just continue to use the 15-40...a good compromise between the 10-40 and 20-50 mentioned in the manual, and change monthly. this small mill, with it's very small oil capacity doing double duty, would do better on this sched, than say the m-1 5-40 and extended drains..kinda be like putting a 1000 dollar saddle on a 100 dollar horse. i believe this little motor was designed for frequent changes due to it's lack of a filter, extending the oci's just because a syn sued here might not be a good idea imho. penz

 

[penzdude]

eiron, that ought to be a great little conversation piece too. man, i have seen more cb honda's, kz kawa's, gs, zook's, and xs yammies than ever before being ridden, obviously out of retirement due to the cost of gas sky rocketing. some of these things look new, having been restored to like new cond, and some others, pristine from loving care and nice garages and covers etc. some others, well,...lol. saw a nice restored honda cb 750 this past sunday at a custom chopper dealer grand opening...cool as you know what!

 

[rokky]

I had two of those years ago. The family had a blast with them. I killed them with kindness. Changed oil every two or three weeks depending on how much riding we were doing. I always used 20/50 Castrol. Those little motors work hard and get very hot. Despite all the miles we put on them they never used oil between changes. I think any good quality 15/40 or 20/50 would work. Frequent oil changes are a must on those little guys.

 

[Eiron]

Hey guys, thanks for the info!

Here's a little more of my thought process:

Blake,
The insolubles & wear metals are exactly what I'm trying to address with the syn oil. I know how much better this oil (Delvac 1) is at mitigating insolubles & reducing wear, so I should be creating less of both along the way. Considering this lower-level contaminant generation, the oil should both last longer & protect better.

penz,
Yeah, I know what you mean (the saddle comp). But I'm looking at it from the other end: if a better saddle fits both me & the horse better, then we're both more comfortable (less chafing, rubbing & hot spots) & less fatigued (more sustained power) over a longer period of time. So even if the horse is a nag to begin with, I still want it to be the best old horse that it can be!
And yes, it's been a big hit with both work & business associates. (I'm especially surprised at all the positive responses from women!)

rokky,
Heat is another reason for switching to syn. Although I shouldn't have to worry too much about it right now (it's typically around 35°F when I leave in the mornings, with my coldest ride at 22°F so far), the better lube should help keep engine temps down. This, in turn, prolongs the life of the oil & helps prevent wear much longer than a regimen of conventional oil.
_____________

It's not worth sending in a UOA to find the best OCI for this scoot, but I really don't want to have to change the oil every 30 days throughout the winter. FWIW, the C70 BB folks say that current premium 15W-40 oils (vastly improved from the 10W-40s available in 1982) should last at least 1,500 mi between changes.

Let me know where my thinking is flawed, & thanks again for the help!

 

[penzdude]

eiron, i don't think your thinking is flawed at all. i think everyone here, whether they are driving a scooter, lawnmower, mc, car or truck is looking to use the best possible lube for their application. if a syn makes you feel more comfortable in your honda, by all means go for it. i think that since the very small amount of oil to begin with has to do double duty, and the engine has no real filter to speak of, that using a realativly inexpensive oil, changed often, might be a alternative to using a syn and trying to extend the drain intervals. i'm sure both idea's have their pros and cons, see what most on the c70 boards are saying and either go with what seems do have served them well, or what makes you feel more comfortable. good luck and watch out for those cagers!

 

[Eiron]

Hey penz,

All the guys willing to give opinions over on the C70 BB say to do short (500-1,500 mi) OCIs with Castrol GTX. (I used to use GTX (& then Syntec) for over 20 yrs, but I now believe there are better options.) When I proposed extending OCIs with PAO syn, one or two guys said they used syn but didn't extend the OCIs, & a few others said they'd be interested in my results.

My view of syn is that it should be used to extend drains because it protects so much better & holds up so much longer. Here's (sorta) the way my thinking's gone:
1) The manual states 1,250 mi OCIs using 10W-40 oil technology from about 25 yrs ago.
2) The "guru" on the C70 BB says modern-day 15W-40s have no problem lasting 1,500 mi OCIs.
3) This means a "fair value" Grp3 5W-40 syn (Rotella Syn) should easily go another 500 mi for a 2,000 mi OCI.
4) And this finally brought me to a high-end Grp4/Grp5 5W-40 syn like Mobil 1. Better film strength, better shear strength, better add pack, better cold flow, better heat resistance, cooler operating temps, less particulate generation... I'm thinking this oil could last 3,000 miles. That's really only double of what a Grp2+ 15W-40 is suggested to do. Since I'm riding this scoot so much, that'd be about 3X/yr.

I guess I'm gonna try this out & see what happens. The C70 guys are telling me that shifting degrades when the oil's used up, so I'll use that rule of thumb. (I've already noticed that it degrades with sub-freezing temps using fresh 15W-40.)

Thanks for the help. Oh, what's a "cager"?

 

[penzdude]

car driver! lol, penz

 

[asiancivicmaniac]

Does anybody know how many quarts of oil these scooters hold? My parents have one and we're going to take it out of storage and have some fun with it so we were thinking of changing the oil, emptying the gas, and changing the spark plugs. Anything else we should do? When we put it into storage two years ago it didn't work so hopefully we can get it working. Anybody have the name of a good forum where I can find more info on these scooters? Thanks.

 

[road_rascal]

I believe the CT70 has an 0.82L sump (0.87 qts). Not much capacity.