Lost 700 rpm somewhere

by Michael Regan in 2 Stroke Technical Questions 12 years ago

Page 4 of 5

Start
Prev
1
2
3
4
5
Next
End

Re: Lost 700 rpm somewhere

by Michael Regan » 11 years ago

Michael Regan

5 96 0

High Peter, no I have not yet found a fix. Thought I did but it came back again.

Yes, yours is identical to mine... right down to the last 1" of throttle being useless. For me, I can tell by ear the slight difference between what WOT sounded like before and what it sounds like now. At its best it sounds more high pitched at WOT and climbs 500' per minute better. At one point I changed the fuel filters, reco'd the fuel pump and the carbys, and cleaned out the fuel lines and replaced ALL fuel with fresh. (Used replaced fuel for lawn mower) I also did a few other minor things I cant recall at the minute, but it did seem to fix it for a while. Since then I done about 10 hours and it's back again. At the minute I am tolerating it as it will still climb at 800' per minute and tack off in my small strip. Now though I am having over heating problems and am wondering if the two are connected. I suspected a slight cold seizure but yesterday ruled that out with a end-scope inspection.

I did also purchase a Tiny Tack and it showed 100 rpm lower than my existing one, which was the opposite to what In was hoping. As I remember, I did a cable check and found the throttle was working properly with both carby cylinders reaching the highest point as it should do. The cylinders where also still moving up during that "useless" last inch of the throttle, so I ruled out the cable completely.

Tell me Peter... are you also having higher engine temps while the EGT's are normal?

Mike

Report
Re: Lost 700 rpm somewhere

by Michael Regan » 11 years ago

Michael Regan

5 96 0

Yep Nick, there is a discerning difference to the keen ear that suggest full WOT is not being reached. BTW, what is the correct install for the Tiny Tach... I went once around two spark plug leads ( I think) ... will check again next time I take off the cowl. I suppose if not done right it will read wrong also... what then? We could end up blaming the wrong Tacho.

Report
Re: Lost 700 rpm somewhere

by Nick Axworthy » 11 years ago

Nick Axworthy

16 325 0

Mine is not a genuine Tiny Tach but one of those Chinese copy's....I'm sure it reads correct as I have cross checked it with a laser tach I have...they both ind within 10rpm,

My a/c tach over reads by around 250rpm,

My instructions say 3 or 4 turn around a single plug wire....I would have thought if you wrap around 2 wires if may get confused...but maybe the gen Tiny Tach is different,

I'm sure there will be more guys knowledgeable that me re the Tiny Tach operation to give you advise.

Thank you said by: Michael Regan

Report
Re: Lost 700 rpm somewhere

by Peter Kohler » 11 years ago

Peter Kohler

1 7 0

Mike

When I changed my short block about a year ago, the new block has always run at very high temp 75-90 (see other thread) compared to old which ran at 60. This has never been properly resolved despite trying everything. I got the best result by reducing the coolant/water mix and have now "accepted" that the new block just runs hotter. The new block was happy to rev to 6500

My reduced revs issue now "assists" the running hot issue and prevents the engine from reaching the very high temps that it did before on full throttle

I am beginning to think that somewhere it has had a heat seize (even though the new block has only about 100 hrs) and that this may be the cause of the lost revs...

Anyway for now its runs fine, I just have to put up with the lost full power

Another issue I have noticed, I am sure related, is a much slower response from idle to foot flat full power - like when you abort a landing - this seems to have coincided with the lost revs issue

Peter

Thank you said by: Michael Regan

Report
Re: Lost 700 rpm somewhere

by Michael Regan » 11 years ago

Michael Regan

5 96 0

Peter, interesting you said you had a slow response from idle to foot flat full power. A couple of months ago I had a partial engine failure and after replacing all fuel filters and rebuilding the fuel pump... the problem was fixed. Before I fixed it though, I had the same problem as you with the slow response (after a partial engine failure).

You can follow the thread here... http://groups.yahoo.com/group/avid_flyer/message/35085

Sometimes if I pushed the throttle to fast the engine would actually stop. The reason I tell you all this is because I suspect its all related to the fuel problem. After doing the fuel line upgrade I was able to get full rpm again. A bit later though, I could not the engine because I forgot to turn on the fuel cock ( yeah... freaking idiot) and was pumping the primer like crazy to try and get more fuel in as the engine began to die. Of course after the idiot realized the tap was off the engine started immediately. Problem is though, immediately after this mishap I got the darn low rpm problem back lol. Now I am back square one again :(

Report

Page 4 of 5

Start
Prev
1
2
3
4
5
Next
End

You do not have permissions to reply to this topic.

Title	Category	Replies
Variation in Max rpm	General Tech Discussion	4
914 won’t exceed 3800rpm	912 / 914 Technical Questions	4
914 cuts out passing 5200 rpm	912 / 914 Technical Questions	1
What’s your 912iS idle rpm set to?	912iS Technical Questions	18
What max RPMs should I be seeing?	912iS Technical Questions	3

Lost 700 rpm somewhere

Recent Videos

Safety First!

ROTALK News

Prize Giveaway!

Log In/Out

Login