'85 700E jettet lean for emissions?

[t3rmin]

From what I understand it's de-stroked, more aggressively cammed, and has domed pistons. Has LOTS of pep, that's for sure. They did really well with this powerplant. It's definitely lean down low, which I'm hoping can be corrected with just the mixture screws. And I don't think I've ridden anything more flickable. I just can't say enough about this bike.

I'll probably "leave well enough alone" with the jets...

[Nessism]

Long duration cams are known to trade low end power for high (they are also dirty from an emissions standpoint) thus the softness you feel in the powerband may not have anything to do with lean running.

How is the engine in terms of vibration smoothness? I used to have a ’87 VFR700 and that bike had plenty of getty-up for me, and the engine was wonderfully smooth. A short stroke 700 that likes to rev sounds like fun as long as the engine is smooth.

[t3rmin]

Well I can tell it's lean by the cold bloodedness and slight backfiring when warming up and hanging idle when blipped. I don't expect it to be as torquey as the 750 with cams like this, and I'm OK with that. High-revving power is a different kind of fun. ;-) Redline is 10k on the 700.

The motor still has some of the characteristic GS buzz, but it's much smoother than my 650 or 750. The buzz is really only there when accelerating, once you settle in at speed it's a non-issue. It cruises very comfortably at 80mph all day long, which is most definitely NOT the case with the 750.

Actually my buddy just bought a VFR750 on Sunday but I have yet to ride it. Says it's a really sweet bike so I'm itchin' to check it out.

[kingofvenus]

A buddy of mine bought an '83 750 Interceptor the same week I got my ES. They (the VF) were a tiny bit smoother, one wasn't really faster than the other. Anouther guy I know got a VF700 the first year those came out, they were not as fast as the VF750's or, atleast that one wasn't.

[Mark whiz]

I still have the original test ride articles on the 700's from Cycle World & Motorcyclist at the house and I know they spell out the differences between the 700 & 750. I know it was de-stroked, final gear ratio changed, carb jetting changed, and a few minor differences on things like fork oil level and such. I'm not sure if they used higher lift cams or if they just adjusted the valve timing. I'll have to dig that out tonight and see what it is.

Either way, it is definitely a "cammy" engine. Below 4K rpm it is no "stump-puller" for sure, but once it gets on the cam around 4k, it'll move like a scalded dog. :shock: It has a really light flywheel effect which makes it rather rev-happy............which you have to watch cause I know when I've run mine up to 8K on the tach, it instantly jumped up to the redline of 10K - What a RUSH! :-D

Unfortunately, that rush starting around 4K brings with it more vibration - mine has always buzzed pretty good from that point on. I'm sure replacing the intake o-rings and sync'ing the carbs will help it some now, but it always buzzed pretty good above 4K ever since it came out of the box. So if the older models buzzed harder - that's scarey 8-[

[t3rmin]

I've ridden a 78 GS750, 81 GS650, 80 GS 750 (16v), and 82 GS1100 (8v). All were buzzier than the 700. The 700 is only slightly more buzzy than modern inline-4 sport bikes I've ridden (ZRX, CBR 600F2). It's not a problem at all.

So I adjusted the mixture screws yesterday. All were around 3 turns out already. I think I've got them around 3.5 turns out now for highest idle. Morning starting is improved (less fussy about choke, starts with fewer cranks, almost zero backfiring), off-idle response is a bit better, and idle is improved. Still takes a while to warm up before it'll hold a low idle.

I've never had to turn the mixture screws out that far on my other GSs. I can only assume I'm having to compensate for something else being lean. Pilot jet? Float levels? What do you think?

[slugsride]

I've ridden a 78 GS750, 81 GS650, 80 GS 750 (16v), and 82 GS1100 (8v). All were buzzier than the 700. The 700 is only slightly more buzzy than modern inline-4 sport bikes I've ridden (ZRX, CBR 600F2). It's not a problem at all.

So I adjusted the mixture screws yesterday. All were around 3 turns out already. I think I've got them around 3.5 turns out now for highest idle. Morning starting is improved (less fussy about choke, starts with fewer cranks, almost zero backfiring), off-idle response is a bit better, and idle is improved. Still takes a while to warm up before it'll hold a low idle.

I've never had to turn the mixture screws out that far on my other GSs. I can only assume I'm having to compensate for something else being lean. Pilot jet? Float levels? What do you think?

Did the idle hanging when you blipped the throttle go away? I've had mine since new (leftover-bought in 88), the cold-bloodedness is normal but the backfiring and not holding low idle is not. Mentioned the boot o-rings on your "pics" post because yours has the same mileage as mine, and now I'm doing a top-end job as a result of them leaking.
My idle screws (which still had the caps on) were all between 2 1/2 and 2 7/8 turns.

[t3rmin]

Did the idle hanging when you blipped the throttle go away? I've had mine since new (leftover-bought in 88), the cold-bloodedness is normal but the backfiring and not holding low idle is not. Mentioned the boot o-rings on your "pics" post because yours has the same mileage as mine, and now I'm doing a top-end job as a result of them leaking.
My idle screws (which still had the caps on) were all between 2 1/2 and 2 7/8 turns.

Throttle blip and return to idle doesn't seem quite as snappy as the 750, but it is improved. Actually it's hard to tell because this darn electronic tach is glitchy down low (and up high).

It'll hold a low idle fine once it's totally warmed up (5-10 minutes on choke). I had to significantly turn down the idle screw as adjusting the mixture screws raised the idle quite a bit, and I found a definite "sweet spot" on each cylinder where idle was best, so I'm fairly confident the mixture screws are correctly set, all else being equal.

Backfiring is almost non-existent now. Heard just a few pops on full choke right after starting up, but none after running for a few seconds. Before there was a fairly steady pop every few seconds while on choke during first few minutes of warm up.

Note I still haven't checked the valves. I'm hoping to find time tomorrow.

Intake o-rings are still an unknown. I've got them on order from Mr. Robert Barr and will probably replace them. Intake boots themselves look great. I'm not seeing any extreme intake leak symptoms, the bike runs fantastic, oil temp is fine, and headers aren't blueing, so I doubt I'm in any kind of dangerous lean scenario.

[slugsride]

Throttle blip and return to idle doesn't seem quite as snappy as the 750, but it is improved. Actually it's hard to tell because this darn electronic tach is glitchy down low (and up high).

***Do a search on that problem--when I was trying to find out what was wrong with mine I read a post about a 700 that had idle problems, his eventual fix was a ignition module and he said that also fixed his glitchy tach! Mine never had that symptom.

It'll hold a low idle fine once it's totally warmed up (5-10 minutes on choke). I had to significantly turn down the idle screw as adjusting the mixture screws raised the idle quite a bit, and I found a definite "sweet spot" on each cylinder where idle was best, so I'm fairly confident the mixture screws are correctly set, all else being equal.

Backfiring is almost non-existent now. Heard just a few pops on full choke right after starting up, but none after running for a few seconds. Before there was a fairly steady pop every few seconds while on choke during first few minutes of warm up.

Note I still haven't checked the valves. I'm hoping to find time tomorrow.

Intake o-rings are still an unknown. I've got them on order from Mr. Robert Barr and will probably replace them. Intake boots themselves look great. I'm not seeing any extreme intake leak symptoms, the bike runs fantastic, oil temp is fine, and headers aren't blueing, so I doubt I'm in any kind of dangerous lean scenario.

My boots looked good too (amazing at 22 years!). Getting the bolts out is a real PITA, had the best luck using the bit from my impact in a 5/16 socket and a ratchet, still had to Dremel slot a couple. My o-rings didn't look as bad as Mr. Barr's picture, but they were all hard and flat. When mine started acting up the two center pipes were turning a gold color near the head.

[QuaiChangKane]

I'm late jumping into this party, but I'll share what I know...


Versus the 750, the 700 had longer rods, taller pistons, slightly different cam lift/duration/timing, and different gearing for better acceleration (sacrificing a smidge of top end). In fact, it was only a couple of tenths shy of the '83 750E in the quarter.

I don't recall anything about carburetion changes or valving changes. It seems that swapping the cams (or whole head) and pistons into a 750 motor while keeping the 750 rods will give a nice little bump in compression (plus a few cc's) and slightly more aggressive cams. I'd imagine that a copper head gasket might help a bit here, too...

It stands to reason that the carburetion would be the same on the 700 as it was on the California 750 - same engine, essentially - but CA was at least as strict in 1983 as the Fed was for 1985 as far as emissions go.


I picked up some 700 pistons last year, and am looking for some cams or a complete 700 head. I'll document this if I ever get the parts together. I'm also in the process of rebuilding a set of 34mm flatslides I got from a friend (free rocks!) that were in need of some TLC - my money says that that will be the hot mod. I'll try to do each mod separately so I can share the results for each one individually.

On a side note, I'm also looking at swapping out for a 700 tail, too - no performance gain, but I think it looks far better than the 750 tail with the additional sculpting along the bottom line. The 700 gas tank looks worse, though, even though I think the 750 tank is ugly on its own.

I'm also looking for an 1150 rear wheel (3.5" - PM ME IF YA GOT ONE!!), and am going to try the RaceTech cartridge emulators from a GS1100E in the 750's forks (and sell my first-born for an Ohlins shock ). SS brake and oil cooler lines, plus an aftermarket (larger) oil cooler just about wrap up the mods I've got planned. Well, maybe aftermarket guages, too - but I'm trying to limit my dreaming to a Thou at a time.... :-D




Sorry for the rambling - If you'd like, I can scan some of the GS700 articles I have for the first ride tests of the 1985 model year.



-Q!

[QuaiChangKane]

Forgot to mention....



My bike was very cold-blooded and cranky down low even after warmed. It turned out to be cracked o-rings on the fuel rails that couple the carbs together, causing the bike to run lean. YMMV, but this is apparently a common problem.

Check your intake boots as well, and check for poor connection on your airbox boots.



-Q!

[t3rmin]

Long overdue follow-up, but I bumped up the main and pilot jets one step. Warms up better, idles better, and power delivery is smoother all through the revs (especially the transition at 6k). Better gas mileage too. Highly recommended.

[Griffin]

Long overdue follow-up, but I bumped up the main and pilot jets one step. Warms up better, idles better, and power delivery is smoother all through the revs (especially the transition at 6k). Better gas mileage too. Highly recommended.

What size jets did you install?

[t3rmin]

Lessee, 122.5 to 125 main and 37.5 to 40 pilot if I recall correctly. Got 'em from z1enterprises.com.

Also I found out the stock pilots do NOT have the little holes on the side (VM style), which means I got the wrong ones (BS style). Luckily I also found out it doesn't matter as long as your carbs have the little rubber plugs over the pilot jet tubes. ;-)

I also installed a UNI brand drop-in filter at the same time. Dunno how much flow difference that is, but if you want to duplicate my results, I'd do the filter too (they're cheap).

[Hugh]

My bike was very cold-blooded and cranky down low even after warmed. It turned out to be cracked o-rings on the fuel rails that couple the carbs together, causing the bike to run lean. YMMV, but this is apparently a common problem.
-Q!

Is it possible that bad o-rings in the fuel rails would actually prevent the bike from starting altogether? My carbs have been off numerous times for cleaning and I still can't get the bike to start - even though they are spotless. I wonder if I buy the "Mikuni CV BS series carb O-ring kit" from Mr Barr (http://www.cycleorings.com/) if my bike would start and run again. Everything from his site for our bike would run a total of $22.09 so it's not that much money for what you get, but I hate to throw money at a problem if it won't fix it.

Here is what I am thinking about ordering - is this the right stuff for the 700?

Mikuni CV BS series carb O-ring kit, U.S. Shipping - $12.67 USD
Mikuni CV carb bowl drain O-ring set - $0.01 USD
20mm Stainless Steel fastener set, w/kit - $5.50 USD
Viton Intake O-ring set, large - $3.91 USD
Subtotal: - $22.09 USD

Hugh