poor low end performance :(

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tizdaz

tizdaz

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Hi guys,

i have a new DBXL 2.0 (zen 32) an olimat unsilenced pipe, 10k steel clutch & I'm running Badlands mx43's.

Mid-top end is perfect, low end is a different story, I have it tuned, runs with no issued except for this low end power. Even on loose surface, the wheels barely spin! Climbing steep-ish hills it also seems to struggle until rpm gets high then its as if a powerband kicks in and power is what id expect, but up until then, it runs like my FG used to years ago before I had a tuned pipe on it!!

I cant compare it to stock as the pipe/clutch etc was fitted from brand new. The clutch is an 9500rpm steel one from taylor RC, this one: https://www.taylorrc.co.uk/product-page/fs-steel-clutch-with-ddm-9500rpm .

Ive also lowered the gearing to help with bottom end but didn't make much difference, and i was running MadMax Land G Rippers which are a very big tire, so thinking that might be the issue, as said above, i bought some MX43's and changed gearing. but nope! still the same :( any ideas?

I've messaged the place i bought pipe from asking if its a mid-top end pipe rather than low end. But even so, the low end performance is poor!

any help much appreciated!
tizdaz said:
Hi guys,

i have a new DBXL 2.0 (zen 32) an olimat unsilenced pipe, 10k steel clutch & I'm running Badlands mx43's.

Mid-top end is perfect, low end is a different story, I have it tuned, runs with no issued except for this low end power. Even on loose surface, the wheels barely spin! Climbing steep-ish hills it also seems to struggle until rpm gets high then its as if a powerband kicks in and power is what id expect, but up until then, it runs like my FG used to years ago before I had a tuned pipe on it!!

I cant compare it to stock as the pipe was fitted from brand new.

Ive also lowered the gearing to help with bottom end but didn't make much difference, and i was running MadMax Land G Rippers which are a very big tire, so thinking that might be the issue, as said above, i bought some MX43's and changed gearing. but nope! still the same :( any ideas?

I've messaged the place i bought pipe from asking if its a mid-top end pipe rather than low end. But even so, the low end performance is poor!

any help much appreciated!
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also does this look normal? it looks like the clutch shows are not making 100% contact?

20230402_182422_resized[3206].jpg
20230402_230555.webp
Here's what spark plug looks like, which seems to be all good so the mixture is ok, like i say apart from this issue the engine runs well with no hiccups etc..
 
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All your plug indicates is your general state of tune is rich. It could be many thing why you have a lack of bottom end. Best guess is your too rich down low. Clutch looks a little funky but not the worst I've ever seen. With that high arse clutch it should be blowing the wheels out from under the truck on launch. Could very well be your pipe as well. My bet is still on tune.
 
Seandonato73 said:
All your plug indicates is your general state of tune is rich. It could be many thing why you have a lack of bottom end. Best guess is your too rich down low. Clutch looks a little funky but not the worst I've ever seen. With that high arse clutch it should be blowing the wheels out from under the truck on launch. Could very well be your pipe as well. My bet is still on tune.
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I think i have it tuned up, if I try go leaner on low needle then performance drops, there's very little smoke (infact there is no smoke!) at all when running, I thought this might be because running too lean but again, if I try richen up, performance drops, so I'm pretty sure ive got the engine dialled in best I can for the low end. For now ive refit the stock clutch and thrown a 10k spring on, maybe the all-steel clutch could be the issue, so will see when I try it out on Friday. Failing that then it has to be the pipe!? ..I was thinking the air filter might be restricting air flow, but ive watched a lot of vids of guys running there's with stock filter/tuned pipe with no issues, so I don't think its the filter.
 
I had to adjust pop off on a dbxl 2.0, the tuning window was extremely narrow and any bit of tuning to get it to be more agile was pointless. That carb is giving you trouble.
 
First, it's not a nitro and with and decent 2 stroke oil, there won't be any smoke, besides start up and possibly till its up to temp.
I run the fs steel clutches in everything for years now. You'll know real quick if it's slipping.
It's hard to give advice not being there, so you'll need to bear with us. What exactly is it doing? Bogging? Cutting out? Act like its flooding?
Transition from idle to wot should be pretty seamless and tuning one shouldn't majorly affect the other. Sure they high and low has some cross over, but it shouldn't be enough to adjust the low screw and it totally throws off the high screw.
Take a video of it and post it to you tube then post the link here. It's about the best way for tuning via internet. Vs actually being there to see what it's doing. For all I know you have a carb issue like rep mentioned and no way to tell you what to check or look for.
 
@tizdaz what pipe are you running? Interesting to see you use a stick style transmitter.

Sounds like the tuning can go leaner on the low end and it's not getting up on the pipe meaning you have zero transition from low to high. Also seems like you blip it too much for the transition to happen.
 
I concure with rep. Tune sounds pretty good, maybe a tad fat but not bad. You don't really have the room there to let it get the rpm up to take advantage of the pipe. Transition starts to sound promising, then you run out of room amd need to let off the throttle. It's pretty difficult to run these rigs without some nice open area, or low gears to let the engine get on the pipe in the smaller area.
 
hi guys, right next to this there is a long stretch of road where i was opening her up while tuning, like i say, low end there just isn't the power i was expecting, on my previous largescales (FG's) with a stock 26 & tuned pipes (dom/FG Steel / Samba etc) they would take off as soon i open the throttle with wheels spinning & dirt flying etc!, but with this, I'm running a zen 32 & an olimat unsilenced pipe & 19T pinion! so it should definitely be kicking up the dirt low end, but there is just hardly any power low end, but then all of a sudden about 30%> throttle its as if ive hit the nitro boost! it takes off & screams.

Yeah i thought the tuning was ok, to be honest thats the one thing i seem to do pretty good :D its the driving i have issues with! lol.

Will get more footage over the weekend with speed runs then you will see/hear the difference from low end to top end. Ive refit the stock clutch with 10k spring but not tested yet so will see how that pans out also, ive kept the 19T pinion on to see how it is. If there is no difference after this weekend i may pick up another pipe to try incase it is something to do with the pipe, how likely would it be that i have a faulty pipe ? :s
ive just found another vid from same day which has more footage of low end (doughnuts etc!) or lack of! ...im just uploading it now :)
here you go:

a good example is right at 19secs in vid, from a stand still to around 30% throttle there is just hardly any power, and at 29secs thats the throttle over 50% and its struggling to even spin the wheels on all that loose dirt & engine sounds like its bogging/struggling just doing simple spins
www.tizdaz.co.uk/temp/PXL_20230325_172040941.TS.mp4
 
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It's definitely 100% not the olimat pipe, I can stand by that along with everybody else here that has one. Bud I'm gunna say you need to adjust your pop pressure immediately before you do anything else. @Seandonato73 has write ups about it and can also walk you through it or I can as well. You need a vacuum/pressure hand pump and a good set of nail clippers.
 
This is my hobby shop friend and I traded him this 5ive t. This is a stock 32 with an 8k spring and an unsilenced olimat pipe. I also adjusted the pop pressure on this carb. Just skip to the running footage.

 
Rep732 said:
It's definitely 100% not the olimat pipe, I can stand by that along with everybody else here that has one. Bud I'm gunna say you need to adjust your pop pressure immediately before you do anything else. @Seandonato73 has write ups about it and can also walk you through it or I can as well. You need a vacuum/pressure hand pump and a good set of nail clippers.
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So it could be the carb? its pretty much brand new and it was running like this from the 1st time i fired it up :( ?
Clubin said:
Try stock tires? Those tires are heavy!
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Yeah i thought it might be the wheels/tires also, so i Ive fit some Badlands MX43's also, still the same buddy.

Rep732 said:
This is my hobby shop friend and I traded him this 5ive t. This is a stock 32 with an 8k spring and an unsilenced olimat pipe. I also adjusted the pop pressure on this carb. Just skip to the running footage.

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Yeah thats kind of how i was expecting mine to run to be honest espcially the low end, my FG ran very similar to this on stock 26 with tuned pipe so its damn annoying that by dibby is running like this with a 32 and olimat pipe :/
 
Please take my advise, the dbxl 2.0 you saw me fix had the same issue with extremely poor low end and if I adjusted it any leaner it would bog and run like crap.
 
I agree it's a pop off pressure issue. They're set way too high for our use. Remember these carbs were originally designed for lawn mowers and chain saws.

If it were an old carb I'd say your metering diaphragm is going bad.
If you adjust the pop off pressure I highly recommend installing the spiral diaphragm at the same time.


There's also a small chance you have an exhaust leak, is your manifold gasket good and flex clamp tight?
 
HXRC said:
I agree it's a pop off pressure issue. They're set way too high for our use. Remember these carbs were originally designed for lawn mowers and chain saws.

If it were an old carb I'd say your metering diaphragm is going bad.
If you adjust the pop off pressure I highly recommend installing the spiral diaphragm at the same time.


There's also a small chance you have an exhaust leak, is your manifold gasket good and flex clamp tight?
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These carbs were designed for hobby engine use, not saws or any o.p.e. this is per conversations I've had with wlabro techs. Although the engine we currently use have their roots based on o.p.e. engines they have long since departed having much in common other then being 2 stroke. (Most, 4 stroke and 4mix are fairly prevalent.)

Unfortunately with the pop pressure this seems to be a reoccurring issue. Unfortunately walbro no longer makes those specs available, however around 20psi works well for our application.

I'm a fan of the spiral diaphragm. Some guys arnt, tuning can be a bit different and they can be a pain to get set up right.

Any leak, intake or exhaust could cause running issues, however in this instance I doubt it's any of the above. Seems to be strictly a fuel issue.
 
Seandonato73 said:
These carbs were designed for hobby engine use, not saws or any o.p.e. this is per conversations I've had with wlabro techs. Although the engine we currently use have their roots

Unfortunately with the pop pressure this seems to be a reoccurring issue. Unfortunately walbro no longer makes those specs available, however around 20psi works well for our application.

I'm a fan of the spiral diaphragm. Some guys arnt, tuning can be a bit different and they can be a pain to get set up right.

Any leak, intake or exhaust could cause running issues, however in this instance I doubt it's any of the above. Seems to be strictly a fuel issue.
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I guess I should have said their "roots" are from saws. Yes, walbro has made changes to improve them for our use. Such as bore, venturi size, jet size, choke options, spiral diaphragm, different metering springs, etc. However, it really depends where you get the carb. "Clone" carbs seem to especially have issues. Walbro makes the correct metering spring, but only few carb models/sources actually have it in the body.

Still agreeing it's a fuel issue, just gave the suggestion because it's an easy check and I don't remember it being mentioned. Maybe it will help someone else.

OP exhaust leaks are usually easy to see visually, oil, soot, or smoke near the gasket surface. Intake leaks can be tested by spraying around the intake/carb/isolator with starting fluid or carb clean and listening for a change in idle.

Also, too small of an idle gap with too lean of a LSN setting could have this effect.
 
Unfortunately walbro seems to be using whatever metering spring they have on hand. Pop pressure isn't a spec for the wt series of carbs. They just have to hold 22psi (don't quote me in that, it may be higher) basically indefinatly. Typically I've seen them over 30psi on new in box walbro carbs. In stock form the pop pressure doesn't really matter. Remember wete fuling engines that make all of 3.5hp. Once you start modifications the fueling needs increase. Then the pop pressure begins to matter. It seems the older carbs were set much lower from the factory then in recent years.
The great metering spring kit you used to be able to buy from walbro has also been very difficult to get, even individual parts for carbs have been impossible to source. Just the society we live in today. If it doesn't work just throw it out.
 
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