X6 Hustler Bogging at Speed

[Suzukidave]

Emailed a friend who knows T20's and his first thought was remove the air filter and test run the bike to see if it makes any difference ..if it doesnt do anything at least its a easy test

[Tourmaster]

Just before I head out to the rally, had enough time to run through the needle settings. I have a bit of egg on my face, and an explanation as to why my right side seemed to be running a bit richer. My left side needle was set to the OEM middle clip setting ... but when I double checked my right needle, the previous owner had set that clip one notch lower ( thus higher than left side)? Missed this detail as I cleaned my carbs one at a time ... let's call it a seniors moment.

Although these original needles look okay, I installed the identical, but new Wemoto needles and set them both to the middle position. Thus, just leaning up the right side a bit.

Took her out for a rip, and was quite pleased with the overall performance. Even as the bike warmed up, was still able to cruise at 70 mph ... with hardly any bogging, and no evident surging at all. Brought the bike back into the shop and raised the clips one notch to see if further leaning things would be even better. I'll do some plug chops next week ... but I'd say she's damn near there. Pretty sure she'll now cruise all day at 65 - 70 mph at 1/2 throttle with room to spare.

One final performance improvement I strongly believe will come with the new insulators. Since I was able to give the bike a real high speed workout this time ... there was lots of big bubbles rising up out of both float bowls once back in the shop. Once I get the new insulators installed, I'll let y'all know if the carb boil off issue is also resolved. Bike runs awesome when cold, but even with this jetting improvement, runs slightly less sprightly when toasty.

Again, thanks for the help guys.

[Tourmaster]

Finally I got the new carb insulators, so decided to do some before and after temperature readings on the head and carb bowls. With the old insulators still in place, went for a rip. Got her well warmed up cruising at 70 mph out on the back road. Pulled over and got cylinder head readings in the 250 to 240 degrees F region. This was with the heat gun lazer pointed right at the base of the spark plugs. Then took a reading of the carb bowl temps and got about 110 degrees F on both.

Went back to the shop and installed the new OEM carb insulators ... then out for another rip. Under the same conditions there was a negligible difference in readings for both the cylinder head and bowls. Conclusion ... the original carb insulators were not an issue. It's still interesting, however, that as the bike sits for a few minutes, the temp of the carbs rises and the bubbling up through the clear fuel lines resumes. I can only assume that this is normal for these bikes?

With the engine fully warmed up, throttle slides open ... compression readings were 135 and 130 on the left and right cylinders respectively. I assume that these are good numbers, but would appreciate some feedback.

I'd also appreciated some comments on whether cylinder head temps in the 250 degrees F are reasonable for these engines.

As I mentioned previously, the bike is running pretty well right now ... so am pretty much ready to strip her down for chroming and painting. One final test that I have in mind will be the leak down test to check crank seal integrity. Still not suspecting the inner seals, as the transmission oil has stayed up after about 200 miles of test runs. I know my cylinder base gaskets are leaking slightly, so I may have to do two leakdown tests ... before and after base gasket replacement ... to get a final definitive reading on the seals.

I'm a raw rookie with leakdown testing ... but have watched a few on-line videos to get a feel for it. I assume that I can just purchase appropriately sized expandable rubber plugs for the intake and exhaust port and rig up some method of pumping (through spark plug hole), holding and reading low pressure (6 psi) drop over time on the system with the piston at bottom dead center.

[Vintageman]

Tourmaster,

I am not sure where you are with this (how it is running), but my impression is the bike runs OK until you run it harder, gets hot... power fades. Reminds me of my early days with old free air/air-cooled snowmobiles…. Before liquid cooling was the norm
So maybe your problem is the very early bike is simply overheating. Do note as Suz transitioned from the 60s into the 70s they did improve free air cooling, mostly in the head design and lowering of compression some

X6: I do think the bike can shed the heat required of ot driven regularly, some bursts, if everything is spot on.
Some normal easy to correct things that cause extra heat (Haw many miles on engine?)
Too much carbon build up on Head dome and piston crown. There is a reason Suz required periodic carbon removal for the top end every so many miles (3000-4000?).
Scuffs, scratched, and material build up on piston skirts. This causes added friction/heat. You see service manuals showing remove of these spots on pistons and if stuck to cylinder walls. If this exist top end a little more noisy.
Clean Air cooling fins. No oil, dirt oxidation build up.
Mechanical wear (cylinder bore)


Your questions:

Is 130-135 PSI compression OK. Those numbers look OK, but can’t rely on just that. If you had the engine when new, measure it then, then checked as time went on performing the test the same way (first kick versus second kick , versus third increases etc.) The present readings versus new would have more meaning. Right now it just says to me you don’t have a hole in your piston top.

What I have learned, is with ignition off of course, maneuver the kick starter by hand slow and fast. It should feel spring and nice pop when fast , both sides feeling the same. A little slower motion to see if it does not leak down too fast. And, how much does that feeling improve with a little oil added t cylinders.

Leak Down test. If you get the equipment to do this. The next question is what is the specification for change in PSI over time fro that specific engine, for example 5 psi in 3 minutes. This varies per engine and some were specified by factory some were not that I can find. Also specified was what max pressure to use.

Still a good test and better of you can look at seals when doing it for leaks. Center seals always a challenge for me … to prove they are performing like new at least.

Good luck and let us know how you make out

[Tourmaster]

Thanks vintageman. I agree with your comments ... so that is why I posted my compression readings ... hoping someone with experience with the X6's specifically, would chime in. Also, if someone has specific leakdown pressure loss over time info, that would be nice too. I was planning to simply pump each chamber up to 6 psi and time the period it takes to drop to 5 psi? I will give this a go irregardless, as one of our local mech's is willing to loan me his hand pump/gauge setup.

Also, when kicking it over, there is nice sharp pop, and it takes about 7 - 8 kicks to reach max pressure.

I'm not suspecting carbon build-up, as the engine had new rings and cylinder honing, just before it was stored away for several years by the PO. I will verify this though, when I install the new base gaskets. Also, the engine sounds fine ... not making any unusual mechanical noises when cold or hot.

Leak test results will be a while, as I need to source intake and exhaust port plugs ... then I will update.

[Tourmaster]

Finally got my port plugs ... and borrowed the leak test rig from my local shop buddy.

Left (ignition side) crank seal failed miserably. Air pours out of that seal so badly, I couldn't get more than about 3 psi into the chamber hand pumping as fast as possible. It's amazing that the engine ran as well as it did considering this state of affairs. The right (clutch) side seems to be in decent shape, I'm thinking most likely since this seal is in contact with trans oil through the clutch housing.

Here's my leak test rig ... note the intake and exhaust port rubber expansion plugs, plus Posiforce bango bolt inplace and ball check valve working well:


My thinking now is to have the crank rebuilt, in particular installing my four new crankseals. While at it, do a thorough inspection of the other components including the transmission.

However, there is the el-cheapo possibility ... if the left outer seal can be replaced without disassembling the engine? Is this possible? Here's a photo of the culprit:

[Suzukidave]

Good deal the leak down test showed the problem .. looks like the shaft may have been a touch rusty and that just ate up the seal when the engine was run . I have seen posts of guys removing these type outside seals without taking the engine apart by drilling a small hole on 2 sides of the outer edge of the seal and threading in self tapping sheet metal screws . Useing the screws to pull the old seal out and then tap in the new seal with a wipe of 3 bond on the outside edge .

[Tourmaster]

Thanks Dave ... I'll mull that over a bit. I've done the sheet metal screw trick on shifter seals in the past, so might be worth a go. Certainly want to be careful not to damage the bearing behind.

I will check with my local rebuilder who has experience with these bikes ... as I'm still leaning towards doing the "full enchilada".

[GT750Battleship]

Hi,pull her apart & have a good look at everything! There is never a better time to find other "things" that may be on the way out?
Cheers,
GT750Battleship.

[Tourmaster]

Thanks Battleship. After pondering this a bit more, that's what I will be doing. Just talked to one of our local vintage club members, who also was a Suzuki mech for a couple of decades ... and he said the same thing.

[Tourmaster]

Fast forward ... thought y'all might like to see the finished product.















- Rechroming by Fairmont out of Edmonton, Alberta
- Paintwork by Bentley's, Alberta
- Frame powder coating by Muenster Saskatchewan

Replacement parts sourced from; Thailand, Australia, Netherlands, England, USA and, yes, Canada

Engine work included new crank seals and bearings ... truing and balancing also. Top end was also redone with oversize pistons, etc.. Needless to say, no more bogging after warm-up. Thanks again for everyone's input.

[jabcb]

Wow, that looks nice.

[GT750Battleship]

Hi,looks terrific...enjoy !!
Cheers,
Roger

[Suzukidave]

Its a prize winning looking bike for sure .. do you have plans to show her ?

[Tourmaster]

Thanks guys. On occasion our vintage bike club takes part in a local car show, so it might be included in one of those events in the future. Not high on my priority list though.

Cheers
Bob