X6 Hustler Bogging at Speed

[Suzukidave]

I may have missed it but did you check the pipes to make sure they are clear , we have heard all kinds of stories of critters making there home in pipes and air boxes . Thats another good question hows the air filter ?

[GT750Battleship]

Just a thought..as I previously mentioned,,the carb body's do suffer from heat expansion,as the two isolators blocks between the cylinders & carbs do not stop heat transference after awhile because of age etc...as I say just a thought ?
Cheers,
GT750Battleship.

[Suzukidave]

If all else fails to help maybe its time for a top end leak down test ?

[Suzukidave]

Just a thought..as I previously mentioned,,the carb body's do suffer from heat expansion,as the two isolators blocks between the cylinders & carbs do not stop heat transference after awhile because of age etc...as I say just a thought ?
Cheers,
GT750Battleship.

Good idea .. i was trying to think what could cause this bogging only after its hot ?

[Alan H]

Take the baffles out of the exhausts and throw the wadding away - I reckon it will be full of oily crap. Get some new tape/wadding like this (clicky) and replace after you had a short run without the baffles - yes it will be noisy, but does it still bog?

[Tourmaster]

Wow ... thanks again guys. And I thought there was no hope left.

Pipes ... Good question. I had taken both the headers and mufflers off, banged around and dumped a bunch of oily carbon chunks out, and put them back on. So how do I get the old wadding out, and put the new wadding in? Scratch around with a bent rod? Is the wadding packed between each set of baffle supports (I see there are several chambers)? I'll try running her with no baffle and see what happens after the 20 minute sweet spot !

Air Filter ... The one I have is an OEM unit that is "prehistoric". I've got a new aftermarket 3.5" high X 5" dia. unit on order already. Will probably be another week or two coming by dog team, however.

Carb Insulators ... Looks like I might be able to get new ones, so will talk to my parts guy tomorrow. This is another interesting, and potentially good point. I've noticed when I park the bike after a typically long, and hot, run ... there are tiny air bubbles rising up out of the float bowls, heading back up towards the petcock area. Bonus of having clear fuel lines to spot this. Anyways, could this be my float bowl fuel boiling a bit??? Certainly worth exploring with new insulators.

Leak down test ... Could do, but the gaskets between the jugs and crankcase are weeping oil ... so the cylinders have to come off anyways. I planned on checking the cylinders and piston clearance anyways, and doing a rebore/oversize if warranted.

Really appreciate all your thoughts and feedback on this guys. Again, I'll keep y'all posted. Cheers

Bob

[Suzukidave]

Lots of things to check for sure but the leaking cylinder base gaskets could be a head bolt torqueing fix .

[GT750Battleship]

Bob, If its leaking between the cylinders & crankcases it's sucking air ?
can only get worse as temperatures rise ! As Alan_H suggested,all two strokes need a clean exhaust system,& exhaust ports,if they haven't,the performance will suffer greatly. The baffles should be removed & heated with a propane torch to burn off oil & carbon,taking care not to get them to hot as they will be damaged,tap them with a screw driver or something as they cool to loosen carbon deposits. The wadding Alan was talking about is on the end of all new baffles..& held in place by wire. I doubt it would still be there on an old T20..!! I unwrap & throw it away on any new baffle that I buy..just something else to restrict exhaust gases & build up carbon & sludge !
Regards,
GT750Battleship.

[Tourmaster]

Perfect ... thanks guys ... I'm no longer down in the dumps with these great comments. Can't do anything about the leaky base gaskets right now. I've already retorqued the head bolts to 15 ftlbs, and that didn't help the leak. I know this has to be fixed, but want to finish eliminating all these other issues.

I will install new insulators ... even my friend mentioned his BSA ran like crap when hot ... until he changed out his old insulators. So this item has good potential.

Great info on the wadding ... and yes, as far as I know there is no wadding left on my baffles. Will follow your clean-up advice.

Won't be able to respond to this stuff for about a week now, as we're off to a vintage motorcycle rally in Alberta. Will post as soon as I have an update though. Thanks again, you guys are the best.

[GT750Battleship]

enjoy the rally,a break from you current bike problem will be welcome I'm sure!
Cheers,
GT750Battleship.

[Tourmaster]

Okay, so I'm back from a couple of vintage bike rallies ... and some supplies have arrived in the interim. Cleaned out the header pipes and mufflers and installed new exhaust header crush gaskets and muffler to header seals. Actually, the exhaust system wasn't really that bad, but made absolutely certain that there were no issues with this aspect.

Then I removed the old air filter and installed the new aftermarket one. So at this point, I presume that the engine should be pretty free breathing from both the intake and exhaust side.

Took her out for a rip, and pretty much have the same issue. Seems like every time I improve things, the bike runs just a bit better ... but no cigar ... still bogging a bit once fully warmed up.

At this point, I'm still waiting for my new carb insulators ... local Suzuki dealer has them on back-order, but says they will have them soon ... another week or two perhaps. I also just received some OEM B77HC NGK plugs so will pop those in next. Once I have these test rides completed, shall give you guys another update.

Discussed the bikes performance at our recent vintage rallies, with some of our more seasoned 2 stroke veterans. Excluding the ever present possibility of needing new crank seals ... one other suggestions was made concerning the condensers. It was argued that perhaps my condensers might be weak, and starting to breakdown as things heat up. The most experienced Suzuki mechanic in our group, felt that this was not likely since my bike wasn't missing ... rather simply bogging down, but still firing smoothly even when toasty. Thus reducing the likelyhood of a condenser issue in his opinion.

As always, comments/suggestions are welcome. As I move further along with all this "easy stuff", the crank seal replacement and rebore items loom large.

[Suzukidave]

Crank seals can be tested with a leak down test , a bit of cost to set up for the test but a whole lot easier and cheaper than a engine tear down . You did say you had the proper main jets installed ?

[Tourmaster]

Dave ... just to recap, the T20 OEM main jet size is 95. Early on in the testing my plugs were running very dark brown and a bit sooty. I'm currently running one size smaller, 90's, and they are no longer sooty. This change also improved the performance at high speed and the plugs are just dark brown. It was also suggested at the vintage rally, that I might consider dropping the needles (raising clip one notch). I'm thinking my jetting/carbs are fairly close now though, as the bike runs great, even at high speed, until it gets hot ... then the high speed bogging returns.

With regards to a leak down test ... I've been putting this off as I work through other items. Another recap ... I have cylinder base gaskets that weep oil a bit after high speed runs. After I try out the new carb insulators, guess I'll be moving on to the leak down test phase. This is uncharted territory for me but I see some excellent you-tube videos, so trust I can pull this off.

Since my base gaskets weep a bit, I may have to replace these babies before I get a final true read on the crank seals. May have to waste a set of base gaskets to determine crank seal condition. Also, not sure if I can remove the cylinders with the engine in the frame?

[Suzukidave]

Put a wrap of masking tape around the throttle grip and mark reference marks on the tape for idle , 1/4 , 1/2 and full throttle . When riding and warmed up check the mark on the tape to see just where the throttle is when the bogging is happening as this will help sort what circuit in the carb the problem could be coming from . .

[Tourmaster]

Okay, so based on my masking tape gradations, at highway speed (6th gear @ about 60 mph/4500 rpms), and the engine warmed up, the bogging starts at the half throttle position. Also, I installed the new OEM B77HC plugs for this run. I killed the throttle and shut her off just at the bog transition point and pulled the plugs. Left cylinder was a nice beige, while the right one was just a bit darker brown ... no soot on both, and otherwise clean. One other thing I noticed (and have noticed before) is that the engine exhibits a bit of a surging effect, just at the bog transition point ... much like the brakes are being lightly applied on and off ... then as you apply even more throttle the bogging effect becomes steady.

I should also mention that the weather this morning was cool with high relative humidity (even started to sprinkle as I returned to the shop, for example). Although the bog effect did return, the cool moist air resulted in one of the bikes best performance runs.