BOG (engine dies snapping throttle open @ low revs)

Hey Guys,

Here is another problem I am having. When I try to give the bike full throttlle (or anything over half throttle) from a low to mid rpm, it will just die. I have to slowly twist the throttle to get the rpm's up without it dying out.

Is this a trait of not having a carb with an accelorator pump? I did remove the bowl off the carb and use some carb cleaner to remove any possible debris or varnish. It didn't really help. It seems like a lean condition occurs, but how do you compensate? I had written a post about my spark plug being black and it was said in a reply that my jet and needle may be worn causing the rich mix. So I am not sure which way to go on this one. Unless my float level is set too low causing a slow start-up and the needle and seat are worn cauing the black plug?

Could this possibly be a symptom of mis-adjusted valves?

This is a very bothersome problem, ya can't get power when you need it most---like going over whoops, my front wheel just falls in the holes.

thanks,
Mark Piechowski

I think you still may have to look at the carb some more. There is a chance that you may have a stator problem as well. What does your spark look like with a new plug in it and someone kicking it over?

F.E.
Does dicking with the idle mix affect the dying from idle? It is dead easy to do and if it makes it better or worse it may indicate mixture problems in the low end fuel circuits.

I have similar problem, but nowhere near the same extent you have. Richening the idle helped a tiny bit, but I suspect mine is with the higer airflow circuits.

Hi,

it can also be that the engine gets wrong air.
Have a look at the intake manifold. Maybe there is
a tear.
If not, I would examine the carb. Clean the float chamber, all jets and holes.

greetings

hribman

Mark,

If your plug is black it's a sure sign you've got too rich a mixture in there. It is also shown by the bogging to a certain extent - but this shows it is probably really rich. This is providing you've done some time on the plug?

The best thing you can do is strip down the carb and have a good look through the jets - taking them out and cleaning them - and replacing things like the needle and adjusting the float level.

Try this first and let us know how you get on.

Round or flat slide carbs have never been the best in terms of response when whacking the throttle open and do require a slightly more elegant throttle opening that that of, say, the vacuum carb. But never to such a degree as that you're describing and never worth any concern.

HTH
Simon

How old are the needle and needle jet? Maybe they cause the wrong jetting because they are worn. I don't have a pumpercarb either just the old Dellorto but it works perfect for me. So perfect that I have the FCR still on the shelf!!

well, I removed the carb and took everything apart. The needle and jet appeared to have no wear marks what so ever. I cleaned everything, there was still some dirt in there from the last time when I had only blown through the jets with gum-out. There is an o-ring seal under the mouth of the carb that bolts to the main body. part of this seal was sticking into a hole, but I am not sure if it was a blind hole or not. The needle was on the 2nd from the top. I decided to raise the needle to the 3rd spot. I have a feeling that the blackness on my spark plug that I spoke of before is from engine oil. I had noticed if I let it idle for a while, the engine starts to die down a little as it was loading-up with a rich mix, but when I rev it up a lot of blue smoke comes from the exhaust---worse than a 2 stroke. Then it is clear for a little while again. I think the valve guide seals are just shot, maybe the rings too.

I have the feeling I am going to have to rebuild the top end of the engine. I don't want to risk a bearing going bad or something else coming apart, plus the engine has oil leaks here and there.

How long is the expected life of the crank bearings and connecting rod? That would about double my costs on the rebuild to include the crank bearings and rod. Where should I look to determine if this portion is a necessity yet?

My spark plug is new. It only has some idling around time on it. Not even an hour. I still have to check out the spark quality. Wouldn't the stator either work or not work with no inbetweens?

I didn't not set the float level yet. I will have to do that tomorrow, I found the specs at HMS Motorsports website. Hopefully this will begin to make a difference.

thanks,
Mark Piechowski

Mark
Is your engine breather still connected to the airbox/frame? If so this is a likely entry point for oil into the intake tract, especially if it has recently been upside-downed on the left side.

Hey Brad,

The air box is clean inside. I had cleaned the air filters, wiped out what I could reach from the box and also wiped out the rubber boot from the box to the carb. There was a light oil residue in there which harbored some dust and dirt, which is why I wiped it out. I really think it is the valve seals. Do these bikes ever suffer from oil drain back problems from the top of the head? I am wondering if the oil is flooding around the valve springs making marginal valve seals seem worse.

Mark

Hi Mark,

the smoke coming out of your silencer is more or less than at a 2 stroke bike?
The valve guide seals do not wear out too fast. But if the bike stood in the garage for a longer time period it can happen
that after starting it the seals are going up on the valve shaft because of being drown out a bit.
I rather think your piston rings are not the best. You have to keep an eye on your oil level. When you are riding
with enough oil you shouldn´t matter about loosing some oil. It won´t cause a bearing damage directly. But you have only 1litre of oil in your engine!
Burning some oil is not the reason why your engine dies when you pull the throttle to end position.
That has to do with carb/float/jet settings or a worn needle and needle jet.
And: What model we´re talking about? Wasn´t it a 98 model? 501? Round or flat slide carb? Please write it in top of a new topic, so it´s easier to think about tips, because each model has it´s own characteristics and problems.

greetings

hribman

Hey Guys,

It is a 98 FE 501e. The carb is a round slide 40mm. I am not sure what size needle and jet it is. Wouldn't jet and needle wear be visibly appearant? I also slid my finger nail down the needle and didn't feel any roughness.

Is the needle held stationary in the slide or does it just drop in and only held by gravity?

After I put the carb back together the other day, I had the bike idling in the drive way,, it seems o idle better than before and the throttle response seems better, but it still seems to lean-sneeze and die. I rode the bike around the block and I tried to give it about 3/4 trottle and it sputtered and started to die until I let off. I think it was because the bike wasn't fully warmed up, so the test may not have offered true evidence. The real test will be tomorrow when I go out riding. I believe there will be improvment, but i have the feeling that it won't yet be proper.

I did check the spark quality, it did spark with the electric starter, but it was of mediocre quality. When I kicked the bike the spark was much brighter and I would say it is plenty sufficiant.

The float level was set about 3/16" too low, which seems like it would be far for this small carb.

I have a Big Gun header and muffler on hs bike. The spark arrestor is blown out, do you think that this may have the effect of reduced back pressure and cause this type of running problem?

Another thing I did was to checkk for air leaks in the manifold boot. While the bike was idling, I sprayed some carb cleaner all around it to see if it woud alter the engine idle, annd it did not. So the boot is in good shape.

Remember when cars used to have carburators? Well, this problem feels exactly like a bad accelorator pump, but since that is nonexsistant on this bike I am a little lost.

I really appreciate all the help so far,
Mark Piechowski

from what you have said i am pretty sure it's a fuel/exhaust related problem.

i had a piston/ring/sleeve problem on my 2003 501. it blew smoke after idling like you have described, and used quite a bit of oil (approx 100mL/Hr), however, there was no noticeable difference in performance really.

i ended up with new piston/rings/sleeve. HUSABERG said i had overheated bike. piston had grabbed sleeve and scratched badly. this happened near new and i knew i hadn't had bike hot. i don't know what happened, maybe faulty piston, but from new that bike used oil until they replaced said parts.

have you made any changes to bike recently???? i'm pretty sure you have a carb prob. good luck, i'm sure it'll be something simple and frustrated as you are, you'll laugh later.

Have fun
Jeff

Hey Guys,
I went out riding today. The bike performed better than the first time I had ridden it. But, it seems that anything over 1/3rd throttle and it is lacking sufficiant fuel. I suppose with the Big Gun pipe, I should go with a bigger jet. Which jet amm I changing? the one on the very bottom or that cartrige type jet that is in the middle? I am going to raise the needle to the highest position and see what kind effect it has for tomorrow's riding.

A guy I work with that had ridden motorcross for a long time had said to me something along the lines of that the needle's effect is only found between 1/4 and 3/4 of throttle. Is there anywhere that offers information on tuning of the Dell-Ortos?

Where would I obtain a selection of jets and needles for the Dell'Orto?

I would like to go back to a stock exhaust since it seems like it'd be quieter than the Big Gun system. What do you guys think of the Big Gun versus a stock system?

thanks,
Mark Piechowski

stepping up jet size

I have a 91 Husqvarna WMX 125, it also has a Dell'Orto carb. I looked to see what size jet it has, which is a 192. My Husaberg has a 175. I think I am going to try the 192 in the 'Berg. Do you think this will be too much of a stretch from possibly one extreme to another?

thanks,
Mark Piechowski

Hi,

you can try it, the 175 seems to be a bit too small. Normally
a 190-195 would be ok.
But I don´t think you will feel a big difference. But try it, at the
dellorto carb you have always to try out. There is no standard solution.
Each dellorto carb is different to another.
You should also check your needle jet. It´s the long one underneath the main jet. That should be a DR270.

greetings

hribman :rock:

THe bigger jet made all the difference

I spok last night about changing the jet from the 175 to the 192 I went out riding this morning----WOW, WHAT A DIFFERENCE ! No more popping and sputtering over half throttle, the bikke is definitely faster and predictable.

The only thing left now is the work on the electric starting. It started up this morning with the electric starter. But when it dies on the trail, I hit the button for the elctric starter and it goes like this wah-wah-wah-bing-wah-wah-BANG-wah-wah-thud-wah-wah-POW-dut-dut-dut-dut...then I take off. A lot of backfiring during the starting. What I did notice is that the with the spark plug out checking the spark quality, even with no plug in the cylinder head, he electric starter didn't seem to crank the engine fast enough to produce more than an intermittant spark. Giving a good kick with the kicker resulted in a bright strong spark. Now that the bike runs good, I will deal with that whn i feel like it.

I think the next thing i should do with the bike is find a way to make the seat softer. I have to alternate cheeks after an hour of riding.

thanks,
Mark Piechowski

Check out guts racing, I installed thier "tall soft" seat foam and gripper cover, it made a big difference.

FirstEliminator said:

Is the needle held stationary in the slide or does it just drop in and only held by gravity?

Click to expand...

There should be a plate fits in under the slide spring that covers the top of the needle circlip - is it there?. I think it would be possible to leave it out (or lose it) & think all was OK, however the needle would only be held in by gravity as you say.

After I had written that post about the needle being held in by gravity, I realized that there is something that holds it in place.

How do I get in touch with "Guts Racing"? Do they have a web site? The seat was recovered before I bought the 'berg, I am wondering if he just put a new cover over the old cover---hmmm. Either way something has to be changed about the hard seat---it's like riding a bench.


Mark Piechowski

Guts Racing seat foams and covers

Hi, Mark....
Try this Guts Racing seats , should take you right to the seat foam page. The web site is Guts Racing.