Help with troubleshooting GS450

[Arek]

Perfect! Will give it a go.

Thanks Steve.

[Arek]

Hi All,

A little late I know, but I owe you a follow-up for all the help provided.

After changing the coils, caps and cleaning the carbs - the engine starts easy and runs much better. Still need to fiddle around with the mixture screw and probably the K&N pod-filter does not improve things. So I have a color-tune tool to figure out if the mixture is OK.

Thanks guys,

[pete]

Good news, glad to hear it!

[Arek]

Alright guys - I need some more help.

Carbs cleaned + synced, electrical harness re-done completely from scratch.

Issue:
It starts really easy and idles fine, but still does not take throttle very well. I can get it to full throttle, but have to play around with the throttle a little before it goes all the way up. Turning the handle all the way from idle does nothing (as in it pretty much stays in idle for a while before it revs up). 1/4 throttle revs it up fine - sounds like jetting or too much air to you?

What I discovered today:
The exhaust is cracked on the right cylinder. The crack is hidden as it sits at the part coming out of the cylinder, but when I place my hand in front of it I can feel gas shooting out. This of course has be fixed, but can this uneven balance on the exhaust create these throttle issues? Would be nice to know before I trouble-shoot myself into pieces.

Bonus info:
The engine has been completely redone by myself. All bearings, piston rings etc. have been changed, and anything which measured out of Hayne's limits was replaced. The valves + valve seats polished with valve paste, and new shims put in to adjust valve clearance. So unless I did something wrong, the engine should be fine.

[LAB3]

So engine gone through means you have compression, ignition gone through and checked means you have spark so that leaves fuel is your next hurdle. Considering that you have pods instead of a stock airbox my first best guess is jetting. Since I've always run my stock airbox I cannot give any sound advice other than most folks like to use the dynajet kits to get them the parts the carbs need to run right with pods. As to a mismatch caused by the exhaust leak, I'd get it patched by whatever means, you're going to want to do it either way.

[Gorminrider]

This of course has be fixed, but can this uneven balance on the exhaust create these throttle issues? Would be nice to know before I trouble-shoot myself into pieces.

as Lab said. really I'd do this FIRST. You had the exhaust off to do the engine so I won't need to warn you to be gentle with the bolts there. A temporary fix might be possible if you want to know this is your main issue...(jbweld and a piece of epoxied muffler tape) but really, with the trouble of all that, I'd get another one or take it somewhere and get it done better.

just as an idea: Your CV carbs need an airpressure difference to lift the needle- manifold pressure should drop when you open the throttle- if your needles and slides don't lift ,it won't. Your Slides may not be functioning or your engine is not sucking correctly with valve timing or exhaust leak.

[Arek]

So engine gone through means you have compression, ignition gone through and checked means you have spark so that leaves fuel is your next hurdle. Considering that you have pods instead of a stock airbox my first best guess is jetting. Since I've always run my stock airbox I cannot give any sound advice other than most folks like to use the dynajet kits to get them the parts the carbs need to run right with pods. As to a mismatch caused by the exhaust leak, I'd get it patched by whatever means, you're going to want to do it either way.

Yes it runs with pods, or rather one big pod covering the two carbs. Image below. It should operate like the stock airbox, but I'm sure it doesn't, so looking for a 2nd hand org. airbox. Hopefully that's all what's needed.

Screenshot 2020-03-26 at 18.55.18.jpg

as Lab said. really I'd do this FIRST. You had the exhaust off to do the engine so I won't need to warn you to be gentle with the bolts there. A temporary fix might be possible if you want to know this is your main issue...(jbweld and a piece of epoxied muffler tape) but really, with the trouble of all that, I'd get another one or take it somewhere and get it done better.

just as an idea: Your CV carbs need an airpressure difference to lift the needle- manifold pressure should drop when you open the throttle- if your needles and slides don't lift ,it won't. Your Slides may not be functioning or your engine is not sucking correctly with valve timing or exhaust leak.

Regarding the manifold pressure, valve timing etc. I figure that could not be the case since I can rev it all the way up, just need to apply 1/4 throttle, then 1/2, then full. Or am I mistaking?

Regarding that exhaust - yes that needs to be done either way.

Thanks so far!

[Big T]

Yeah, too much air.
Try putting tape around the filter, blocking half of it off
See if that improves your throttle response

[Gorminrider]

^^^that's a good idea and easy too. Not a pod guy myself but You might just need richer jets...people fiddle with the idlemix screw too...and of course whatever jets you do have MUST have been properly cleaned when you took the carbs down...that means removed and the tiny holes cleaned to "see-through"

[Arek]

Yeah, too much air.
Try putting tape around the filter, blocking half of it off
See if that improves your throttle response

Big T you're a genius! This was what was needed. I actually ended up taping almost 80% of it over, see image below And maybe it's running a bit rich with that setup, but I haven't tried less or more tape. The filter is not oiled either, and that will probably make a difference too.

Now, I risk getting my head bitten off, but would there be anything wrong in finding the sweet-spot % of tape cover over the filter, and make that a more permanent setup? I have a ColorTune I can use to find the perfect amount of black, strong tape. I know it is a bit rudimental, but if it work it works!

Screenshot 2020-03-27 at 17.18.56.jpg

[LAB3]

Big T you're a genius! This was what was needed. I actually ended up taping almost 80% of it over, see image below And maybe it's running a bit rich with that setup, but I haven't tried less or more tape. The filter is not oiled either, and that will probably make a difference too.

Now, I risk getting my head bitten off, but would there be anything wrong in finding the sweet-spot % of tape cover over the filter, and make that a more permanent setup? I have a ColorTune I can use to find the perfect amount of black, strong tape. I know it is a bit rudimental, but if it work it works!

[ATTACH=CONFIG]60617[/ATTACH]

Sooner or later that tape is going to fall off, those types of things tend to happen in a cold rain at 3am. Chances are I'd do the tape thing for the meantime and put off the rejet kit until everything else was up to snuff and the cash was easier to justify.

[Gorminrider]

maybe hoseclamps and a cut-up bleach bottle or 5 litre oil bottlewould do it more permanently..and adjustable even! Thing is you'll want to trial it riding...