|
|
Post by sidney81 on Jan 29, 2021 21:22:59 GMT 1
Hi everyone ,some may of seen I'm building the 250 air cooled hybrid ,I need some advice pointers with the jetting please .so it's 250 had the heads mechined and re profiled squish set to Just over 1 mm, ports cleaned up ,carbon reeds ,some pipes from Martin Johnson ,and stock carbs and will have ram air foam filters, now jetting I've not got clue where to start !! Anyone any ideas please and thanks ,Chris 👍
|
|
|
|
Post by geoffb on Jan 30, 2021 0:26:17 GMT 1
Hi Chris,
I am in a similar position with my RD350LC 4L0 with RamAir foam filters and have learned a lot from searching this forum for previous advice.
I intend to start with larger main and pilot jets and work down to avoid potential seizures, checking the plugs and timing as well of course. I did this back in the 80s but have forgotten most of it having had 4 strokes for the last 30 years. 😉
Good luck and I will be interested in seeing how you get on.
Cheers
Geoff
|
|
|
|
Post by 4l04ever on Jan 30, 2021 0:54:40 GMT 1
The air filters affect the fuelling loads. Maybe go for 50% bigger mains and pilots to start with??
|
|
|
|
Post by sidney81 on Jan 30, 2021 7:23:44 GMT 1
Hi Chris, I am in a similar position with my RD350LC 4L0 with RamAir foam filters and have learned a lot from searching this forum for previous advice. I intend to start with larger main and pilot jets and work down to avoid potential seizures, checking the plugs and timing as well of course. I did this back in the 80s but have forgotten most of it having had 4 strokes for the last 30 years. 😉 Good luck and I will be interested in seeing how you get on. Cheers Geoff thanks Geoff , everyday is a school day hey ,yes lots of guys on here with great help !! |
|
|
|
Post by sidney81 on Jan 30, 2021 7:24:55 GMT 1
The air filters affect the fuelling loads. Maybe go for 50% bigger mains and pilots to start with?? hi there ,50% bigger hey ok sounds good 🙂 |
|
|
|
Post by steeley on Jan 30, 2021 11:57:24 GMT 1
Hi , i would start out with a larger main to start with . The other jets ,pilot ,needle, needle jet maybe pretty close . You need to get it run in and have a large enough main jet to prevent engine damage . Had a couple of melt downs/pistons over the years but that's another story . When the engine is run in the best route is get it on a dyno .
|
|
|
|
Post by sidney81 on Jan 30, 2021 12:21:46 GMT 1
Hi , i would start out with a larger main to start with . The other jets ,pilot ,needle, needle jet maybe pretty close . You need to get it run in and have a large enough main jet to prevent engine damage . Had a couple of melt downs/pistons over the years but that's another story . When the engine is run in the best route is get it on a dyno . Hi ,yes ok so large main to start with ! Like you say it's on fresh bores so I will have to run it in nicley first , yep agree to get the best out of it Dyno is the way to go , would be great to get it booked in with mutts . |
|
|
|
Post by 4l04ever on Jan 30, 2021 18:38:10 GMT 1
The pilot jets will also need to be increased, as the air filters increase airflow at all throttle positions. My LC runs a modified airbox and my pilots had to go up a size.
|
|
|
|
Post by midlifecrisisrd on Jan 30, 2021 18:46:21 GMT 1
I'd say to start with up 2 sizes on pilot and add 100 to what main is standard
As in standard 31k 22.5 and 240 to 27.5 and 340
Steve
|
|
|
|
Post by geoffb on Jan 30, 2021 18:57:59 GMT 1
|
|
|
|
Post by tony2stroke on Jan 30, 2021 20:01:48 GMT 1
People are giving jet sizes for LC carbs, don't you have air cooled VM28mm carbs on, or are they LC carbs ?
Also you need to go up quite a bit on main jet if those are Martin77 pipes, I think I had to go up 50 for my Martin pipes alone, (that was on a RD200 with 250Lc carbs and manifolds with pod filters on) and then the extra for the filters.
You may be better asking about jetting this on the aircooledrd site.
But as has been said start really rich and drop down from there.
|
|
|
|
Post by sidney81 on Jan 30, 2021 20:32:49 GMT 1
People are giving jet sizes for LC carbs, don't you have air cooled VM28mm carbs on, or are they LC carbs ? Also you need to go up quite a bit on main jet if those are Martin77 pipes, I think I had to go up 50 for my Martin pipes alone, (that was on a RD200 with 250Lc carbs and manifolds with pod filters on) and then the extra for the filters. You may be better asking about jetting this on the aircooledrd site. But as has been said start really rich and drop down from there. Hi ,yes the are the VM 28 s I was just after some pointers in the right direction to get me going 👍 |
|
|
|
Post by midlifecrisisrd on Jan 30, 2021 20:45:42 GMT 1
Surely same principal as both Mikuni Vm's and same jet number system
Wouldn't be adding 100 to a Keihin PWK main jet for pods
Steve
|
|
|
|
Post by steeley on Jan 30, 2021 21:11:53 GMT 1
Hi , i think the std main jet size is 115 so plus 50, 165 . You need to start some where . I had an Lc with an f2 tune with 26mm carbs foam filters and Nikon pipes 290 mains . I ran it like this for years ,but one day i fitted some 310 main jets and it was no good unless you were wide open in 3rd and 4th gear . In the finish i went to 270 mains with no problems . Also what you could do is give Rob Pemberton a call at Skellerns Motorcycles 01242 583031 he has some knowledge on most things 2 stroke .
|
|
|
|
Post by sidney81 on Jan 30, 2021 21:13:21 GMT 1
Hi , i think the std main jet size is 115 so plus 50, 165 . You need to start some where . I had an Lc with an f2 tune with 26mm carbs foam filters and Nikon pipes 290 mains . I ran it like this for years ,but one day i fitted some 310 main jets and it was no good unless you were wide open in 3rd and 4th gear . In the finish i went to 270 mains with no problems . Also what you could do is give Rob Pemberton a call at Skellerns Motorcycles 01242 583031 he has some knowledge on most things 2 stroke . Thank you very helpful 👍 |
|
|
|
Post by tony2stroke on Jan 30, 2021 21:32:43 GMT 1
Hi , i think the std main jet size is 115 so plus 50, 165 . You need to start some where . I had an Lc with an f2 tune with 26mm carbs foam filters and Nikon pipes 290 mains . I ran it like this for years ,but one day i fitted some 310 main jets and it was no good unless you were wide open in 3rd and 4th gear . In the finish i went to 270 mains with no problems . Also what you could do is give Rob Pemberton a call at Skellerns Motorcycles 01242 583031 he has some knowledge on most things 2 stroke . Yes I think your right 115 or 120 standard for the aircooled vm, so if 50 higher for LC carbs just for pipes then that is 25% I think, so by that logic roughly 30 higher for your carbs, then extra for ram air filters. Probably worth ringing Martin or email him for advice, he is a really helpful guy, I remember him warning me to up jet a lot or get hole in piston. |
|
|
|
Post by sidney81 on Jan 30, 2021 21:38:33 GMT 1
Hi , i think the std main jet size is 115 so plus 50, 165 . You need to start some where . I had an Lc with an f2 tune with 26mm carbs foam filters and Nikon pipes 290 mains . I ran it like this for years ,but one day i fitted some 310 main jets and it was no good unless you were wide open in 3rd and 4th gear . In the finish i went to 270 mains with no problems . Also what you could do is give Rob Pemberton a call at Skellerns Motorcycles 01242 583031 he has some knowledge on most things 2 stroke . Yes I think your right 115 or 120 standard for the aircooled vm, so if 50 higher for LC carbs just for pipes then that is 25% I think, so by that logic roughly 30 higher for your carbs, then extra for ram air filters. Probably worth ringing Martin or email him for advice, he is a really helpful guy, I remember him warning me to up jet a lot or get hole in piston. I speak with him most days ,he is very helpful I like him alot ,he's not to sure on the jetting he said to ask about for some info as he's not to familiar with the air cooled carbs etc 👍 |
|
|
|
Post by tony2stroke on Jan 30, 2021 21:49:43 GMT 1
I have an old article from a mag showing a tune recommended by Yamaha for track use back in the day, the part about airbox was take the top chamber off and put some gauze over the inlet of what is left to stop stones getting in, they then recommend a 210 main jet (190 standard) so that's about 10%, I used this equation sorta on my bike 220 main with pod filters, it ran great, then 50 extra for pipes which tallies with steelys bike, others I have noticed on here have upto 290 mains for pods, so you see its not that simple, but going by what I used 10% extra for filters and 25% for Martin pipes, you want 35% exrta, That's my tuppence worth
|
|
|
|
Post by sidney81 on Jan 30, 2021 21:58:03 GMT 1
I have an old article from a mag showing a tune recommended by Yamaha for track use back in the day, the part about airbox was take the top chamber off and put some gauze over the inlet of what is left to stop stones getting in, they then recommend a 210 main jet (190 standard) so that's about 10%, I used this equation sorta on my bike 220 main with pod filters, it ran great, then 50 extra for pipes which tallies with steelys bike, others I have noticed on here have upto 290 mains for pods, so you see its not that simple, but going by what I used 10% extra for filters and 25% for Martin pipes, you want 35% exrta, That's my tuppence worth Sooooo ha ha what size main you you have a go with Tony ? |
|
|
|
Post by tony2stroke on Jan 30, 2021 22:23:00 GMT 1
I have an old article from a mag showing a tune recommended by Yamaha for track use back in the day, the part about airbox was take the top chamber off and put some gauze over the inlet of what is left to stop stones getting in, they then recommend a 210 main jet (190 standard) so that's about 10%, I used this equation sorta on my bike 220 main with pod filters, it ran great, then 50 extra for pipes which tallies with steelys bike, others I have noticed on here have upto 290 mains for pods, so you see its not that simple, but going by what I used 10% extra for filters and 25% for Martin pipes, you want 35% exrta, That's my tuppence worth Sooooo ha ha what size main you you have a go with Tony ? If you had LC carbs I would have said start at 290 main, but its aircooled, my equation would say if 120 standard main then 35% extra would make it 45 extra ish, 165 main, but as its first try another 10% or so, about another 20, so 185/190 ish start, but just to be sure if you have them try 290 and see what happens, the jetting on the LC is different to aircooled as you have the balance pipe to take into account. The 35% equation is the same jetting for 2 of us here so far. There is a lot to take into account here, the aircooled runs hotter, that alters the air density of fuel mixture and other things that go over my head, I would just use the equation above for Martin pipes and pod filters, but its your call mate, I don't want you to get a hole in your piston, equally I don't want to be the cause of you spending on loads of different jets. 1 thing sure if you try 290 main you will know straight away which way to go. |
|
|
|
Post by sidney81 on Jan 30, 2021 22:28:14 GMT 1
Sooooo ha ha what size main you you have a go with Tony ? If you had LC carbs I would have said start at 290 main, but its aircooled, my equation would say if 120 standard main then 35% extra would make it 45 extra ish, 165 main, but as its first try another 10% or so, about another 20, so 185/190 ish start, but just to be sure if you have them try 290 and see what happens, the jetting on the LC is different to aircooled as you have the balance pipe to take into account. The 35% equation is the same jetting for 2 of us here so far. There is a lot to take into account here, the aircooled runs hotter, that alters the air density of fuel mixture and other things that go over my head, I would just use the equation above for Martin pipes and pod filters, but its your call mate, I don't want you to get a hole in your piston, equally I don't want to be the cause of you spending on loads of different jets. 1 thing sure if you try 290 main you will know straight away which way to go. Thanks Tony ,I'd also never hold anybody responsible if the worse happens 👍 |
|
|
|
Post by tony2stroke on Jan 30, 2021 23:32:02 GMT 1
Here is a link to the Mikuni manual site, excellent reading, help you understand the carb, scroll down to the VM manual and download, free and safe. www.mikuni.com/c-manuals.html |
|
|
|
Post by steeley on Jan 31, 2021 9:23:39 GMT 1
Hi Chris , as Tony says if you put 290 mains in and went up the road you will know right away if they are to big .
|
|
|
|
Post by sidney81 on Jan 31, 2021 10:39:48 GMT 1
Hi Chris , as Tony says if you put 290 mains in and went up the road you will know right away if they are to big . Thanks bud , 👍 yep cool it's a learning curve ,it's just the initial starting point ! |
|
|
|
Post by 4l04ever on Jan 31, 2021 15:40:17 GMT 1
Try the Aircooled forum, as there maybe someone there with a similar engine setup with foam filters.
|
|
|
|
Post by sidney81 on Jan 31, 2021 16:18:25 GMT 1
Try the Aircooled forum, as there maybe someone there with a similar engine setup with foam filters. Yep thats a good call 👍 |
|
|
|
Post by sidney81 on Mar 7, 2021 9:07:06 GMT 1
Hi everyone,the jetting battle is still going on !! I got a set of pwk 28 s of mutts he jetted them roughly to what he thought would be a start ,138 main and 38 pilot !! Put them on and it wouldn't run off choke! Not at all so I put a 48 and a 50 in as it's all I had in the spears box and it ran better off choke but still cuts out when you rev it ,so I've got some more jets I've started big I've put in some 58 s and it runs ok ish but when you ride it it's not happy didn't want to rev above 4 k ,it's not cutting out it's just boggy if I ease the throttle off it seems to run better!! Trouble is I'm not sure if it's still lean or now to rich!! I'm running it in to so can't give it the beans yet !! Any ideas lads ? I appreciate it's difficult to say without seeing it running !! Chris 🙂
|
|
|
|
Post by midlifecrisisrd on Mar 7, 2021 12:09:00 GMT 1
I'd guess if it's boggy and runs better on smaller throttle openings I'd say the main is too small
Steve
|
|
|
|
Post by Tobyjugs on Mar 7, 2021 13:10:59 GMT 1
That's what I think as well Steve.
I would up the mains and go down on the pilots
|
|
|
|
Post by sidney81 on Mar 7, 2021 13:29:11 GMT 1
It's very wet out the pipes to to point it's spat oil all over the workshop wall , it won't rev past 4 k when riding it it's spitty and spluttery I thought it could be rich ? On the mains ??
|
|
