Raizer Posted October 27, 2020 Share Posted October 27, 2020 What model Rotax is it? Some have both cylinders firing a the same time so single port would be no issue at all. 1 Quote Link to comment Share on other sites More sharing options...
Raizer Posted October 27, 2020 Share Posted October 27, 2020 Twin cylinder called for twin post? Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted October 27, 2020 Author Share Posted October 27, 2020 18 minutes ago, Raizer said: What model Rotax is it? Some have both cylinders firing a the same time so single port would be no issue at all. Its a Type 373, they made them for like 22 years, but i'm failing to find much info on them. https://www.rotax.com/en/100-years/historical-vehicles-engines/detail/type-373.html Quote Link to comment Share on other sites More sharing options...
Truenotch Posted October 27, 2020 Share Posted October 27, 2020 Jet Skis run a single spanny on twin cylinder engines, so it must work. 2 1 Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted October 27, 2020 Author Share Posted October 27, 2020 11 hours ago, Truenotch said: Jet Skis run a single spanny on twin cylinder engines, so it must work. I never even considered that both cylinders might fire at once. Surely a spanny would only work if they did fire at once? Quote Link to comment Share on other sites More sharing options...
Truenotch Posted October 27, 2020 Share Posted October 27, 2020 2 hours ago, Vintage Grumble said: Surely a spanny would only work if they did fire at once? I thought the same, but just looked up the engine above and they look to be 180 out... . Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted October 27, 2020 Author Share Posted October 27, 2020 ITS ALL A HAVE, an elaborate ruse to sell tune pipes! As far as I understand, a tune pipe wont do dick if its taking opposing pulses from two cylinders, unless how I think tune pipes work, is not how tune pipes work? I'll have a look and see if the ports are separate in the head itself, because twin tune pipes hanging out the back would be amazing. Edit: Yeh nah yeh, that wont work. 1 Quote Link to comment Share on other sites More sharing options...
tortron Posted October 27, 2020 Share Posted October 27, 2020 theres 3 cyl snowmobiles running 3 into 1 pipes. But id suggest its a space and cost factor and triple spannies would go hard Quote Link to comment Share on other sites More sharing options...
M.H. Posted October 27, 2020 Share Posted October 27, 2020 Outboards run upto 8 cylinders into the one exhaust tuner, it's not exactly a spanny but it's a tuned length cone so would be doing the same Quote Link to comment Share on other sites More sharing options...
anglia4 Posted October 27, 2020 Share Posted October 27, 2020 I would think that for a single spanny to work it would be a matter of getting the length right so that the pulse is sent from one cylinder and received by the next. Fuck knows how that would work in reality, the pulse would have to have a half length return time I guess otherwise the pulses might cancel each other out. 3 Quote Link to comment Share on other sites More sharing options...
h4nd Posted October 27, 2020 Share Posted October 27, 2020 Dai manifold. Seems to work OK. Add trombone slider for tunability? 2 Quote Link to comment Share on other sites More sharing options...
keltik Posted October 27, 2020 Share Posted October 27, 2020 What if you put a valve on the exhaust for each cylinder? Then you could use a blower for forced induction, shave the head by half an inch and replace that pesky spark plug with a unit injector. Its the only 2stroke design i'll accept. 2 1 Quote Link to comment Share on other sites More sharing options...
Popular Post Vintage Grumble Posted October 28, 2020 Author Popular Post Share Posted October 28, 2020 So last week I tidied up and fixed a few things. First thing was the gas cap, I opened it and touched the rubber seal, and the peened retainer broke off and fell in the tank, ha. I managed to tap the cap, so I could bolt it back together. I cleaned, painted and made a new seal for the guts of it. Next I rerouted and cleaned up the wiring, but I'll eventually go through and redo a lot of it, as it's all Barry spec crimp on terminals and the like. Next I tried to clean the steering wheel, but it ended up as a repaint job (it's pretty bright, but closer to the seat shade now). I also rotated it on the boss so it's up the correct way. I removed a big ugly bracket, and replaced it with stainless washers to make it prettier. And the steering doofer looks near new! I also cleaned up the switches a bit too. Next I made some water outlet things from stainless bolts. One for the bilge, and one for the tell tail. I put both on the drivers side, so I can see what's happening. I also put the tell tail in easy reach, for hand spec temp checks. Anyways, on Monday I took it to Bonnydoon with Keltik and Keltik snr. It took a bit to get it started (just need to learn the correct choke/throttle ratio) but once going it ran really well, and didn't leave me disappointed with its power/speed, as I was quite worried about that. BUT, after say 5 mins of blasting around, it slowly lost power. The engine note didn't change, it just got slowly more gutless. I found if I went back to just over idle for a few mins, and then gunned it, it would run good again, but only for a few minutes. It would also run on when I went to turn it off. I thought it might be too lean (needle was set to max lean), so we tried moving the needle richer, but it wouldn't even run on anything but the original leanest position. We tried running with the gas cap open incase it was the lack of a breather, but that made no difference. We checked the jets and cleaned out the bowl, but all seemed OK. We didn't remove the float needle, but there was speculation from some, that the flow through it open didn't seem enough, but I wasn't keen to pull this apart in the lake, so went home. I hope to have a fiddle and try again this weekend. Action shot from Keltiks vessel, 13 1 Quote Link to comment Share on other sites More sharing options...
sheepers Posted October 28, 2020 Share Posted October 28, 2020 im going to suggest crank seal are fucked. 2 Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted October 28, 2020 Author Share Posted October 28, 2020 1 hour ago, sheepers said: im going to suggest crank seal are fucked. That could be a possibility. So you think its sucking in air and leaning out, and then getting too hot, thus causing the loss of power and running on? Hmmmmmmmmm. The last owner had recently changed the bearings and seals, so may have cocked something up, Barry's will Barry. We were thinking the float was emptying out due to lack of fuel flow (due to smutz in the float needle) and putting around gave it time to refill. I'll clean out the carb, and work on making sure the flow of fuel is as good as it can be, and if that fails to fix it, I had better replace the seals. Quote Link to comment Share on other sites More sharing options...
sheepers Posted October 28, 2020 Share Posted October 28, 2020 the symptoms you describe are classic leaking crank seal type shit, thats why im thinking it might be that. does it have a breather in the crank case? you could put a bolt in it so it cant suck in from the crankcase and that might tell you if the seals are shit. classic scooter trick that one, crank seal fucks out, chuck a bolt in the breather and your good to go (a short distance before it shits itself properly) 3 Quote Link to comment Share on other sites More sharing options...
h4nd Posted October 29, 2020 Share Posted October 29, 2020 Plug chop and pic when it's running weird pls? Quote Link to comment Share on other sites More sharing options...
Truenotch Posted October 30, 2020 Share Posted October 30, 2020 Softening off once it warms up could also mean it’s too rich. Too rich often means it’ll run mean as when cold, but will be a bit flaccid once it warms up. Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted October 30, 2020 Author Share Posted October 30, 2020 1 minute ago, Truenotch said: Softening off once it warms up could also mean it’s too rich. Too rich often means it’ll run mean as when cold, but will be a bit flaccid once it warms up. Dats true, but rich wouldn't cause the running on issue, and it needed a lot of choke to start, so I'm thinking it's more of a lean issue. I cleaned the carb out, but didn't see anything really. I got new spark plugs, and have managed to squeeze a 1/4 fuel filter onto the 3/16 hose, along with a free flowing tap, so will see if that makes any difference. 1 Quote Link to comment Share on other sites More sharing options...
Thphantum Posted October 30, 2020 Share Posted October 30, 2020 On 28/10/2020 at 22:43, Vintage Grumble said: So last week I tidied up and fixed a few things. First thing was the gas cap, I opened it and touched the rubber seal, and the peened retainer broke off and fell in the tank, ha. I managed to tap the cap, so I could bolt it back together. I cleaned, painted and made a new seal for the guts of it. Next I rerouted and cleaned up the wiring, but I'll eventually go through and redo a lot of it, as it's all Barry spec crimp on terminals and the like. Next I tried to clean the steering wheel, but it ended up as a repaint job (it's pretty bright, but closer to the seat shade now). I also rotated it on the boss so it's up the correct way. I removed a big ugly bracket, and replaced it with stainless washers to make it prettier. And the steering doofer looks near new! I also cleaned up the switches a bit too. Next I made some water outlet things from stainless bolts. One for the bilge, and one for the tell tail. I put both on the drivers side, so I can see what's happening. I also put the tell tail in easy reach, for hand spec temp checks. Anyways, on Monday I took it to Bonnydoon with Keltik and Keltik snr. It took a bit to get it started (just need to learn the correct choke/throttle ratio) but once going it ran really well, and didn't leave me disappointed with its power/speed, as I was quite worried about that. BUT, after say 5 mins of blasting around, it slowly lost power. The engine note didn't change, it just got slowly more gutless. I found if I went back to just over idle for a few mins, and then gunned it, it would run good again, but only for a few minutes. It would also run on when I went to turn it off. I thought it might be too lean (needle was set to max lean), so we tried moving the needle richer, but it wouldn't even run on anything but the original leanest position. We tried running with the gas cap open incase it was the lack of a breather, but that made no difference. We checked the jets and cleaned out the bowl, but all seemed OK. We didn't remove the float needle, but there was speculation from some, that the flow through it open didn't seem enough, but I wasn't keen to pull this apart in the lake, so went home. I hope to have a fiddle and try again this weekend. Action shot from Keltiks vessel, Quite happy to tow this down to Waikerimoana for you to do a group demo. 6 1 Quote Link to comment Share on other sites More sharing options...
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